In the following post I have explained a simple yet enhanced 12V capacitive discharge ignition system which derives its operating voltage from the battery instead of the alternator for generating the igniting sparks.
Since it works independently from the alternator voltage, without depending on a pickup coil signal, it is able to function more efficiently and consistently, enabling a much smoother ride of the vehicle even at lower speeds.
Contact Breaker Vs CDI
A capacitive discharge ignition unit also called the CDI unit is the modern alternative for the age old contact breakers, which were quite crude with their functions and reliability.
The modern CDI is an electronic version of the contact breaker which uses sophisticated electronic parts for generating the required arching across the spark plug terminals.
The concept is not complicated at all, the section of the alternator provides the required 100 to 200V AC to the CDI circuit, where the voltage is intermittently stored and discharged by a high voltage capacitor through a few rectifying diodes.
These rapid bursts of high voltage discharges are dumped into the primary winding of an ignition coil where its appropriately stepped up to many thousands of volts for acquiring the required arcing, which ultimately functions as the igniting sparks across the connected spark plug contacts.
I have already discussed the basic electronic CDI circuit in one of my previous posts, though the circuit is extremely versatile, it depends and derives its operating voltage from the alternator. Since the alternator voltage depends on the engine speeds, the generated voltages tend to get affected with varying speeds.
At higher speeds it works fine, but at lower speeds, the alternator voltage also lowers, this results in an inconsistent sparking forcing the alternator and the engine to stutter.
This inconsistency ultimately affects the functioning of the CDI and the whole system starts getting hampered, sometimes even causing the engine to halt.
The circuit of an enhanced capacitive discharge ignition circuit which is discussed here, eliminates the use of the alternator voltage for functioning, instead it utilizes the battery voltage for generating the required actions.
The Circuit Concept
The whole concept for this electronic CDI can be understood by studying the shown circuit diagram below:
The diodes, the SCR and the associated components form a standard CDI circuit.
The high voltage of around 200V which needs to be fed to the above circuit is generated through an ordinary step down transformer connected the other way round.
The secondary winding of the transformer now becomes the primary and vice versa.
The low voltage primary winding is fed with high current pulsating DC generated by a standard IC555 circuit via a power transistor.
This pulsating voltage is stepped up to the required 200V and becomes the operating voltage for the attached CDI circuit.
The CDI circuit converts this 200V into bursts of high current for feeding the input winding of the ignition coil.
These rapid high current bursts are further amplified to many thousands of volts by the ignition coil and finally fed to the connected spark plug for the required arcing and the initiating the ignition of the vehicle.
As can be seen the input voltage is acquired from a 12V DC source which is actually the battery of the vehicle.
Due to this the generated sparks are very consistent without interruptions providing the vehicle a constant supply of the required ignition sparks irrespective of the vehicle situation.
The consistent sparking also makes the fuel consumption efficient, makes the engine less prone to wear and tear and enhances the overall mileage of the vehicle.
Use a 1K resistor at the base of TIP122...... 100 ohm is incorrectly shown
Synchronizing with Wheel RPM
If you want the above circuit to be triggered by the alternator so that the combustion is ideally efficient and synchronized with the wheel RPM, the above design may be modified in the following way:
A 1K resistor is used at the base of TIP122...... since 100 ohm is incorrectly shown.
The above configuration may be further modified as shown in the following diagram, which appears to be the most appropriate way of implementing the proposed enhanced CDI circuit for all 2 and 3 wheelers.
How it Works
As we know, the reset pin#4 of IC 555 requires a positive potential to allow the normal functioning of the IC 555 as an astable or as monostable. If the pin#4 is not associated with the positive line, the IC remains dormant and disabled.
Here the pin#4 of the IC can be seen connected with the alternator voltage. This voltage can be of any level from the alternator, it doesn't matter, since it is appropriately stabilized by the 33 k resistor and the following zener diode, capacitor network.
The alternator will generate a positive and negative cycle pulses, in response to each rotation of the vehicle wheel.
The positive pulse will be converted into a 12 V positive feed at the pin#4 which will cause the circuit to initiate and stay activated during the entire positive pulse duration cycle of the waveform.
During these periods, the IC 555 will operate and fire the SCR multiple number if times in short bursts, causing the ignition to fire with higher efficiency and for a sustained period of time during the firing angle of the combustion and the piston.
This will also enable the CDI to work in tandem with the wheel rotation generating an ideally synchronized combustion of the engine and with an optimal efficiency.
Finalized Enhanced CDI Design with PWM Control
CDI PCB Circuit
Parts List
All resistors are 1/4w unless stated
1K - 1
10K- 1
POT 10K - 1
100 Ohms 1/2 watt - 1
56 Ohms 1/2 watt - 1
Diodes 1N4007 - 9
Capacitors
1uF/25V - 1
0.01uF/50V Ceramic - 1
105/400V PPC - 1
Semiconductors
IC 555 - 1
Mosfet IRF540 - 1
SCR - BT151
Transformer 0-12V/220V/1amp - 1
CDI ignition coil - 1
Video Clip showing the Test Result of the above shown electronic capacitive discharge circuit system
Another Version of Electronic Ignition
The following diagram provides another version of a IC 555 based electronic ignition system, which I got from an old magazine page:
Here, the left side stage which includes the IC 555, 4 transistors and the X1 transformer, form a 12 V to 500 V step up push pull inverter.
The right side section using the SCR BT151, and the associated circuitry forms the capacitive discharge ignition stage.
The design works with the old contact breaker type of mechanism, for timing the ignition and triggering the SCR.
While the contact beaker remains closed, the SCR remains disabled, and this allows the capacitor C2 to charge via the 500 V DC from the inverter output. Next, as soon as the contact breaker opens, the SCR gets its gate trigger via R9, 10, 11, 12, and C4, and it fires causing C2 to discharge across the attached ignition coil primary winding, which in turn causes the secondary of the ignition coil to produce the required high voltage pulse into the spark plug for the required ignition.
With Pickup Trigger
In modern vehicles we find the contact breaker being replaced with a pickup coil, which ensures a solid state working of the system without any wear and tear. The above electronic CDI design could be also used with pickup coil set up, with the following given modifications.
With over 50,000 comments answered so far, this is the only electronics website dedicated to solving all your circuit-related problems. If you’re stuck on a circuit, please leave your question in the comment box, and I will try to solve it ASAP!
Good evening sir, i made this circuit but even pin 4 of timer ic disconnected from pin 8 still pin 3 has an output is it normal?
Hi Elmar, pin#4 must be grounded through a resistor or directly, only then pin#3 will be disabled.
also, do you have any ideas on how to set up a spark measurement device to measure the strength of the CDI pulse?
For this application, I think you can select one of the circuits given in the following article and integrate it with an LM3915 bar graph LED generator circuit:
https://www.homemade-circuits.com/2-simple-rf-detector-circuits-explored/
Thanks for this article. Can you tell me what the diagram looks like when you add a tachometer feed? i think i know where, but i’m not sure.
thanks.
The above CDI circuits get triggered by an external pulse, which can be from a pickup coil of the automobile or an oscillator circuit such as a 555 astable, so the feed for the tachometer can be also taken from the same external trigger source which drives the CDI pulses.
Hello sir, can i use this circuit as a cdi unit tester?
Hi Elmar, yes, you can definitely do that!
Thank you sir, i also found your circuit design cdi tester.
No problem Elmar, all the best to you!
Let me know if you face any problems with the implementations…
Hello, thank you very much for your articles, I have something to ask. Where will the power from the control coil go in your design? ”Synchronizing with Wheel RPM”
My English is not very good, I hope you understand and answer.
Hi, referring to the following design, the synchronizing input from the wheel RPM must be connected to the point labelled as “6 to 12V from pickup coil”
Thank you for your reply.
I made the CDI AC circuit as you instructed, it works very well, thank you again. But today, when I connected them to the “”Finalized Enhanced CDI Design with PWM Control”” circuit there was no spark. I measured the voltage at the output of the transformer as 374v AC. I used a 12v – 0 – 12v 3A symmetrical transformer, which steps down the voltage from 220v AC to 12v AC (is this a problem?). The circuit ran for about 3 minutes then the irf540 and the 1n4007 diode connected to it burned out. Can you advise me where I went wrong?
I think the MOSFET burned due to high voltage spikes generated from the CDI coil.
You can try replacing the MOSFET with a TIP122 BJT, because BJTs are more dependable than MOSFETs, and remember to connect the 1N4007 diode, either across the collector/emitter of the BJT or across the BJT collector and positive DC of the circuit.
Also, please connect a 100uF/25V directly across the supply terminals of the 555 IC.
Let me know how it goes..
Hello Swagatam, Thank for share you ideas with us. so i have a question regarding the last diagram. so i need to know can i use 12v-0v-12v / 220v normal transformer for it. that means 50Hz/60Hz one? if it can’t which type of tranformer i can use or can you give me the turns for primary and secondary coils.
And other one is can’t i use trigger pickup coil for your second diagram “Synchronizing with Wheel RPM” ? if it can how can i put it.
Thank you!
Thank you Avish,
Yes, the transformer can be any normal iron-core 50Hz/60Hz step-down transformer, you can see it in the adjoining video.
If you are looking for a pickup coil triggered CDI circuit, then you can simply use the diagram explained in the following article, no need to build the above complex design.
https://www.homemade-circuits.com/how-to-make-capacitive-discharge/
Nice article, You have an idea on how to proceed is there is no battery (one a one magnet fly wheel + CDI). The cdi is down and I would like to realise one with a microcontroller for the advance timing.
If there’s no battery then you can use the following circuit:
https://www.homemade-circuits.com/how-to-make-capacitive-discharge/
Sorry, i have no idea how to implement advance timing with microcontroller.
I would like to charge an extra electrolyte in order to serve as power supply for the microcontroller (Pic or aduino nano (or another controller which boots up fast enough)), which would the calculate the delay (in function of the RPM) to discharge the capacity (without discharging the elco).
You can use a 6800uF/50V capacitor after a blocking diode 1N4007, and feed the DC to your microcontroller through a 7805V regulator.
m saying good night from Cuba.
I present my name is Jorge Luis, I have experience and elctronica and electricity of motorcycles: I am interested in making a DC CDI functional for a bike 200cc 4 timpo. Or it could also be a TCI.
Idida TCI, it works me down very well but when I give it revolutions the engine gets stuck.
Since you doylas thank you for your help,
Hi Jorge,
If you have a pickup coil in your bike, you can try the following CDI circuit, and check the results.
https://www.homemade-circuits.com/how-to-make-capacitive-discharge/
Buenas la pregunta es este sistema de cdi le servira auna moto bicilindrica de cuatro tiempos cb350k4
Good day. I was wondering if you have a version of the CDI circuit that only uses 12-15VDC from a battery?
I do not have a magneto nor do I have an alternator.
Hi, The first circuit will work exactly as per your specifications. As long as the circuit is powered with 12V, the ignition coil will keep generating the sparks. The frequency of the sparks will be equal to the frequency of the 555 oscillator circuit
hi sorry a little off exact topic but i crossed activator wire for the kill switch that runs directly to cdi and now my engine wont run. sarter motor was engaged while wire was connected what am i facing for repairs? pick up coil and stator design.still getting good firebut wontfullyhit and run
Hi, sorry, I am not an automobile expert so it will be difficult for me to help you with the situation.
hello swagatam first of all i’m sorry because it is weak in english what is the
receiver coil you are talking about? (is it a module) ?
Can you explain with a diagram how to connect this circuit to my 1991 model 1400 engine honda civic? my vehicle has 4 cylinders and electronic ignition system. There is a module in the distributor, should I cancel it. I am a little confused.
Thank you in advance for your help
Hello Burhan, the circuit explained above is intended for 2 wheelers or 3 wheelers, it can be also used for cars but I do have the full information regarding how to connect it to a car ignition system…you may have to consult a qualified car mechanic for the connection details.
Hello there. First of all, I would like to thank you for sharing really nice projects. here is my question. I have a vehicle with a distributor, it has electronic ignition. How can I connect this circuit you shared to my vehicle? my car is 1991 honda civic with 1/4 engine
Hello, you will have to supply 12V DC to the IC 555 circuit. Next, you can disconnect the red wire which is connected to the MOSFET drain, and connect it to your pickup coil output. Finally connect the high tension wire from the CDI coil with the spark plug.
Hi Swagatam Pl check the circuit of the 555 timer of Finalized Enhanced CDI Design with PWM Control, In which the 3 no. pin should be connected to the gate of the IRF540 and not on the pot. also the Pot should be connected to the pin no. 7 and not on pin no. 3.
Please correct if i am wrong, I made as per the circuit provided but the 555 timer burnt out frequently.
This Why I saying is all other circuits above are having the output 3 connected to the transistor.
Regards
Manish
Hi Manish, Using pin#7 as the output is also correct, but mostly pin#3 is used as the output, since it is able to provide both high and low outputs. Pin#7 can produce only low logic but no high logic that is why we need an external resistor (10K) for providing the gate voltage to the mosfet during the OFF times. That said both pin#3 and pin#7 can provide flip flop or oscillating outputs.
I have myself built IC 555 oscillator using pin#7 as the output and it never had any problems….if you want to use pin#3 as the output, you can very well do it.
An example design can be witnessed in the following article:
https://www.homemade-circuits.com/making-adjustable-electromagnet-circuit/
Dear Swagatam
Can you help/ share the schematics of the 35KV spark tester based on the similar lines. What We require is to test the 35KV spark testing on the low current on some meters. I tried to make you version but in the second tranformer from 220 – 12 volt and 12v to 220 Volt the voltages drop 80volt output and the 555 timer IC does not work.
Can you suggest a better circuit diagram using the car CDI.
Regards
MAnish
Dear Manish, I can suggest the above circuits only which can produce well over 27 kv. Both the designs that you tried are well tested by me (you can check the videos). Since you want the current to be low, a 2 wheeler CDI/ignition coil is the recommended option. All the above circuits are very good and tested by me. This CDI circuit is the one which is used in all bajaj motorcycles and rickshaws
Dear Swagtam : What I have done is converted the 12 V supply from transformer to 12V Dc thru connecting a bridge rectifier and feeding it to 555 timer circuit. the output of the 12 volt transformer is AC and again fed tot he input of the 12 to 220 V transformer , in which I am getting 223V Ac output.
Is it correct or not. Please confirm.
Yes that is correct, and it is the correct method of producing low current 220V for the CDI circuit, as explained in the last section of the above article.
Thanks for your great circuits. I have a Kohler 20HP twin cylinder that recently had the ignition coil fail. What I was hoping I might do is adapt your circuit to file the ignition coil salvaged from a 90’s GM. They use two (or three) coils to fire two cylinders in same manner as the Kohler.
What are the pin numbers of IC555 in the circuit pulled from a magazine. The circuit uses the conventional points for trigger.
Thanks
Thank you, you can surely try any of the concepts presented in the above article.
the 555 stage in the last two diagrams are actually IC 555 astable oscillator designs.
You can incorporate the first design from the following article, and replace it in the last two CDI diagrams
https://www.homemade-circuits.com/ic-555-oscillator-alarm-and-siren-circuits/
what if we add more cappacitance?
I need 125 cc dc cdi unit diagram
Which then goes through a bridge rectifier. There will always be a positive voltage at the anode of the SCR all the time the oscillator circuit is working, so it will never turn off after the initial pulse to the gate.
I’ll take off my modification and see if I can get it to work as you have shown.
There’s no bridge rectifier here, even if we had one, still there would be huge breaks in between to enable the interrupted switching of the triac.
Bridge rectifier doesn’t mean the DC is pure, the DC will still be intermittent, unless a filter capacitor is added.
But how will the SCR turn off?
I checked with circuit simulators and my oscilloscope, but no negative voltage was ever applied to the gate of the SCR to turn it off, and the anode was always kept at a high voltage.
Maybe because I removed the capacitor from the points that I got some switch bounce which affected the circuit. My modifications seemed to have solved the problem but I can’t stop there and will continue to work on the circuit.
As they say, if it ain’t broke, fix it till it is. 🙂
Many thanks for pointing me in the right direction, and for all the projects on your site.
SCR will turn off because the pulses from the transformer or the alternator are pulsating DC, they are not pure DC.
I built the circuit using points, but it didn’t work.
When the gate of the SCR receives a pulse from C4 it conducts, and will discharge C2, but as the high voltage generator doesn’t stop, the high voltage will still be present at the anode of the SCR, so it will stay on even when the gate voltage is removed.
I changed the circuit and put a 4.7K resistor between pin 4 (reset) of the 555 and 12V. This was connected via a 2N2222 to ground. Two 1N4007 diodes were placed in the SCR cathode to ground line to give about a 1.4 volts from the forward voltage drop of the diodes all the time the SCR was conducting and discharging C2. This 1.4 volts went to the base of the 2N2222 via a current limiting resistor, keeping the 555 turned off until C2 was fully discharged and the SCR had fully turned off.
Not sure why it did not work for you, it worked for me though, you can see this in the video.
Hi
I think your battery powered CDI circuit could be the answer to my problem. I have built an electric starter for my Honda XR650R but it does not crank it over fast enough to make a spark. It make a spark when kicked over. Would it be possible to supply the CDI from the battery when starting then when running use the standard system. Please let me know your thoughts I am a novice with electronics.
Kind Regards
Tim Bungay
Hi, surely you can try the second concept, by using a 1k resistor across pin4 and the positive line through a series press button.
While starting the bike you can keep this switch depressed so that the sparking becomes continuously available at the spark plug while cranking the petrol suction system. Once the engine ignites you can release the switch for the normal operations
Thank you thank you very much God bless you, my son will be able to enjoy his toy
No problem, wish you all the best, and I hope your son enjoys the project, and succeeds with it!
Let me know if you have any further problems!
Hello Mr. Swagatam!
Thank you very much friend, I will hope that you correct all the diagrams and I will make sure that they are all correctly synchronized with the alternator and the RPM of the vehicle, I wait for you, and that my son is waiting for him, he is excited, thank you very much thank you we wait.
No problem Mr. Jose, You can view the second diagram, it has been updated as per the discussed synchronization with the wheel RPM.
Please let me know if you have any further questions!
Hello Mr. Swagatam!
I recently got a 50cc 2-stroke motorcycle bike for my son. The system I had is a CDI that is powered by the 12v AC generator and it does not have a pulse signal, I wonder if this circuit can be used to update the one it has, besides that it would have to change for that to work, in the same way that you have it but without the pulse signal and that it only feeds from the generator.
Hello Mr. Jose,
Actually every CDI has to be synchronized with the vehicle RPM so that the ignition sparking and ignition combustion resonates with the vehicle speed and RPM.
Although having a battery operated CDI is more efficient, even that must be in sync with the speed RPM of the vehicle.
This feature can be also added in the above circuits by disconnecting the TIP122 base from pin3 of th IC555 and connecting it with the alternator voltage via a 100k resistor.
I will soon correct all the diagrams and make sure all are synchronized with the alternator and the vehicle RPM appropriately.
hello and thank you for putting this site up i was going through it all for past 3 hrs and trying to find a solution to my bike’s ignition problem . it is a 2 stroke twin cylinder with a dc cdi unit as stock equipment and wasted spark on one at all times meaning of the cylinders fires when piston is on BDC and waste and do nothing . it has a single cdi wire feeding the twin coils . when i bought the bike the previous owner ha removed the dc cdi box and re it with a low rpm single cylander ac cdi unit the bike starts runs out of juice at 4000 rpm and do not work with the stock stator electrical supply feeding it since it is made to work alongside with a charged battery…… . how and in what part of the circuit could i boost the power to get to the coils also it has the lighting coils which is not used and could i wire those to the ignition in primary generator to get higher voltage to the cdi box . note that lighting coils put out more amps and lower voltage .. then this bike fires once at 180 degree 2 times faster then this cdi has been design to do . how can get out of this hole . if i can built one then i gotta do it because parts are not available appreciate any help and if the above design could get boosted up to feed a twin coil at 10 k rpm …… thank you
Hi, the core of the ignition coil determines how fast it can be triggered, and here the core is able to tolerate well over 100 cycles per second, which is 6k RPM, close to what is needed by you.
If you use a ferrite cored ignition coil then the triggering could be achieved to any possible limit.
Hi Swagatam,
I have a problem with my old atv Polaris Xplorer 300 because It need a new cdi and because I live in Europe is hard to fiind a new one to be send under 20 days.
Can you help with a circuit for my atv , I am not very good in electronics but I have friends who can help me but i need an specific circuit because my cdi doesn t have trigger and work using just electricity from his coil .
I attach some pics from Polaris service manual with the circuitshttps://ibb.co/71tSxxx
https://ibb.co/88BJ09N
https://ibb.co/DbkmQPq
Thank you in advance.
Hi Otonel, The basic CDI circuit should be the same as given above, and can be applied for your vehicle also. However, the specifications of the various excitation wires are not known to me, therefore assigning those inputs to the basic CDI circuit can be difficult unless the details are exactly provided.
Tengo dudas sobre el valor de las 2 resistencias que van al Triac, me podria decir el valor de la de arriba y de la de abajo. Gracias de antemano
470 ohms and 100 ohms
hi dear sir god bless you ,i have designed some double coil for car and i am in the process of producing unfortunately 30 percent of productions is returned due to problems including leaks and arc from the inside ,
And I’m designing a test circuit for the coils before transferring,
I want to count the number of pulses that reach the candle through the output wire and wireless, that is, by wrapping some wire around the wire plug
((((Please enable an output circuit only to the extent that it activates and deactivates the transistor.))))
Thank you in advance
That I can count the number of pulses through the micro at mega
Hi Sedigh, you can build a Darlington configuration using two BC547. Wrap the base with the output wire through a couple of wire turns. Connect an LED across collector and the positive +6V supply and emitter to negative of the 6V. Make sure to have a 220 ohm resistor in series with the LED. See if this circuits works for you
Hi Swagatom,
I have a single cylinder 2 stroke engine with an A/C CDI it is only has one HV coil that also gives the trigger signal the coil has the charge wire from one end and the trigger wire from the other end. The coil has a resistance of 106 ohms and will generate 130 volts between the Pulse and charge wire when cranking the engine.If you ground the pulse or charge wire it will also give 130 volts (volts measured with aid of a Diode and capacitor) Could you please advise if you know of a schematicto make a A/C CDI for a single coil system
Kind Regards Peter Gale
Hi Ian, as far as I know a typical CDI requires a couple of AC triggering voltages from the vehicles alternator and pick up coil. One is high voltage of around 200V from the alternator, while the other is 12V AC from the pickup. I have no idea regarding the single coil system which you are referring to.
More info here: https://www.homemade-circuits.com/how-to-make-capacitive-discharge/
Does it work on motorbikes? Thank you very much
Yes it is specifically designed for motor bikes….
Hi,
I’m an old retired guy playing with a cool little chinese motor bike. The low rpm problems are my challenge and I Think your improved circuit is my solution. Also I want to fire my ignition with a hall effect sensor mounted on a movable plate using my old mag coil mounting screw holes in association with a new flywheel with a magnet mounted. When my clutch is in, my timing is retarded for starting and idling. As I engage the clutch, the spark advances.(old car, old motorcycle).
This link shows what I have drawn, and I would appreciate your most intense criticism.
https://drive.google.com/folderview?id=1WJ4we9wqDSKL_fTglKFidoGpmqg1V6qH
Rick
Hi, I wish I could help, but since I am not an expert in the automobile field it is difficult for me to assess your ideas.
I am an antique auto and motorcycle restorer, and I’m not having an issue with the mechanics, this is my first pcb and I was hoping for critique on that.
Thank you!
Rick
Hi Swagatam
Is it possible with AC or DC cdi box circuit output high voltage to run DC or AC motor?
Kcool, no that wont’ work, because CDIs have low current outputs
I have an old Tecumseh engine that has the ignition module. The charge coil outputs about 30 to 36 volt ac pulsed, one wire. The pickup is a grounding type contact. There is no 12v dc power available. How can I build a cdi that could replace this?
Use the last circuit in the above page…so you won’t need any external DC to operate the circuit.
Swagatam, I am Dan in the U.S., and your web page contains a lot of exciting information! My question, I am working on a 1970 VW Beetle, Type 1, 1600cc. Of the circuit designs you have posted, or still not posted to the Web, what do you recommend for upgrading my Classic, 4 Cylinder, 4 Cycle Beetle? Thanks! Dan
Thanks Dan, actually the above explained design is intended for 2 Wheelers, I am not sure how this can be modified for a car engine. A qualified motor mechanic perhaps would be more knowledgeable about this.
Swagatam, I do thank you for your reply! As I stated, I am enjoying researching the information that you have posted! My research revealed a circuit titled, “Multi-spark CDI Circuit”. I do believe that this is one that you designed for automobiles. Of which, I am scrubbing the drawings and schematics, (I was not able to locate a Parts List). From here, I do have 2 questions. 1) You note in the schematic, “To Trigger Circuit”. Is this an input from the Points system for Distribution timing? Maybe the Alternator? Something different? Please advise. 2) Near the Coil connections, you have (2) 680k resistors, in series, connected to another component before they reach the path to Ground. I am having difficulty determining what this component is. I read “MOV1S14K 275”. I have no doubt that my interpretation is incorrect. What is this item? By the way, might you have a Parts List you could share? THANKS again! Dan
Thanks Daniel,
The circuit was not designed by me, it was lifted from an expert pdf source. The trigger input is supposed to be from a pickup coil, every vehicle has one I guess. That part is an MOV or metal oxide varistor for suppressing sudden high voltage spike or transient from the ignition coil EMF.
The parts are actually exactly as given in the diagram…all the resistors are 1/4 watt 1% MFR, unless specified in the diagram.
All the capacitors are metallized polyester type rated at 100V except C2 which 1uF/275V,
If you have further problems, let me know I’ll clarify them quickly
Hi sir, thanks for this post, i really appreciate your work and effort. I have some question to ask sir:
1. can this circuit start a generator?
2. Is there any mean to add or connect a toggle switch circuit to it? Such that pressed the generator ignite and start up
Thanks Solomon, this circuit is designed to create sparks only, so I am not sure how the sparks can be used to initiate the generator ignition, because ignition system normally also incorporates a fuel injection system for injecting fuel into the combustion engine for the required combustion.
Thank you for posting this. I am working on a scooter and this will work nicely. I have copper clad board that I would like to make the pcb for this with but I’ve never done one with quite so many parts. Would it be possible for ease of assembly to get a drawing of the traces as you would do them for the final iteration of the ignition module?
I am glad it helped you, however I am sorry, designing the PCB can be difficult due to lack of time. In my free time I may surely try to update it.
I understand. If I find a suitable solution before then I will share it.
https://drive.google.com/open?id=1LeLGL19C6NNNx5M_hcFvfnzAcFLf_3RO
This is my first attempt. Whenever you have a moment to look at it I would appreciate any feedback you have.
Pin#8 and pin#5 connections needs to swapped, same for pin#6 and pin#7 connections, looks like the pin#5 to pin#8 were mistakenly counted in the opposite direction.
Thank you for that. Should it look something more like this then? I also want to double check that I have Q1 and R1 correct.
https://drive.google.com/open?id=12xC_cEH3voubulgAplrj5F24FG_tJdie
Looks OK, although it can be further improved as shown below:
That does clean tings up nicely thank you. Your help was invaluable.
It’s my pleasure!
Also, I think you missed R2 in the PCB, which is very important.
You’re right I did miss that one – How would you suggest adding that?
You can add a pad on pin#7 track, and another pad vertically up connected with the positive line.
Gotcha – thanks again!
????
https://drive.google.com/open?id=1XK5UHQMSZXJhQ2ew10dBBxS-dmTXjZJK
I have this power supply, 220v to 12v – do you think it would be possible to use it for this project?
yes no problem, any DC 12V power supply can be used, current can be 1 amp or higher…
I am looking at the parts list and the diagram and can not see where the 105/400V is intended for. could you help?
Please see the brown big capacitor, and what’s printed on it!
Haha yes I noticed it shortly after I sent that message. The parts list says 10 1N4007 diodes but I only count 9 on the diagram
yes, looks like only 9 are there in the actual circuit, I’ll correct it soon in the parts list, thanks for pointing it out.
Hi! I have a ’67 Fiat 1500 and I’m planning to put a 3D printed rotor with four magnets in the distributor cam, replacing the points with a hall effect sensor (like this: https://www.youtube.com/watch?v=tlj5KYjAVn4 ). The modification by itself is easy to do, but also I’d like to use your CDI system… what modifications should I do to trigger the spark with the hall effect sensor? Would this ignition be powerful enought to work with an automotive ignition coil?
Regards from Córdoba, Argentina!
Hi, you can use the following configuration for your hall effect sensor, and integrate it the CDI circuit shown in the last diagram of the above article:
you can disconnect the red wire from the mosfet drain and connect it with the red arrow shown in the above linked diagram.
The series diode with this red wire is also not necessary and could be replaced with direct link.
yes this design will be powerful enough to work with any ignition coil. If required you may increase the 105/400V capacitor value to 2uF/400V for enhancing the power level.
hi Swagatam, I want to DIY and replace a faulty ignitor module or cdi for 12 volt, 3 cylinder car engine. Are there any circuit in your blog that suitable for me.
I have the photo of the cdi pcb board but i’m not sure about the component they use on the board. I am willing to pay a reasonable price for you to redesign/duplicate it.
Hi Kenny, I am sorry presently I do not have any schematic for car ignition system, but if you can explain the functioning details of the circuit then probably I can design it myself and present it here!
Hey swag,
You have been very helpful on this topic for fixing my seadoo. I have decided to use the circuit that utilizes the battery as my coil does not generate the 220 voltage. Just wondering what the arrows are that are pointed at the 2 resistors on this diagram. Hoping to get this project done this week and get the seadoo back in the water. Also being in canada the 12/220 may be difficult but I read your comment about 6/120 and using the 12V. For a 2 cylinder 2 stroke engine is there anything different I need or will your finalized diagram work? Thanks so much.
Thanks Adam, Those are the symbols for the diodes, which are 1N4007 in this design.
A far as I know, a timed triggering is always required for all ignition based driving systems, therefore in your system also a timed triggering should be incorporated, otherwise the sparking will just go on continuously inside the ignition chamber which may not be good for the system.
Before building and installing you will have to figure out some arrangement for enabling a timed triggering.
In automobiles this is done through a pickup coil, you can perhaps take the help of a qualified auto mechanic for getting this solved for you
I do have a pickup coil that is already part of the ignition system. Also I know which symbols are the diodes I am talking about the small arrows the to top right of the IC in the diagram above. They seem to be pointing to the resistors.
OK I think you are referring to the 1M and the 22K pots, those are potentiometers or variable resistors. You can learn more about them here:
https://www.homemade-circuits.com/potentiometers-pots-explained/
Excellent thank you I just wanted to be sure. I will try and build this before the weekend. The transformer is the hardest part to locate here as the common house voltage is 120V
Thanks Adam, I wish you all the best,
I have updated the finalized circuit and the video showing the test results.
I can not tell where the 12v trigger comes into the circuit on the updated circuit. Could you clarify?
Thanks
Please see the red wire going toward the drain of the mosfet, you will have to disconnect it from the mosfet drain and connect it with the pickup source
Also I know I am asking a lot but is there anyway you could make a parts list so I dont miss any. I found the transformer for 26 bucks! Great deal
Thanks again
I will try to update it soon…
Hi Swag.
I have two cylinders on my motorcycle. Each cylinder has two spark plugs. Can I use the above circuit?
Many thanks.
Joe
Hi Joe,
I am not sure about it, you may have to consult this with a qualified auto mechanic.
Hi Swag.
This circuit is perfect for me.
Can I connect two coils instead of just one?
Regards
Joe
Hi Joe, yes you can but even if you connect two coils both will fire at the same time, will that be OK with your ignition system??
Hi Swag.
Thanks for your prompt response.
Yes, two coils firing at the same time is what I am after.
I will build a second unit to handle the second timing pulse also firing two simultaneous sparks.
So, just to recap.
I can use two ignition coils in parallel or do I need to isolate them some way?
Thanks and regards
Joe
Hi Joe, It is still not clear to me.
You are saying:
“Yes, two coils firing at the same time is what I am after.”
then you are also saying:
“I will build a second unit to handle the second timing pulse also firing two simultaneous sparks.”
both sentences are contradicting.
If your have a “second timing pulse” that means the firing instances are different for the two combustion chambers?
In that case you will require two entirely separate circuits and coils to handle the ignition of the two combustion chambers.
Hi Swag.
Yes, this is correct.
Two timings pulses.
Each timing pulse fires two coils simultaneously.
Your example shows one coil only.
Can I connect two coils to each circuit without any modifications?
Thanks for your help.
Regards.
Joe
Hi Joe,
yes you can do that.
But please don’t try the circuit as yet, because when I recently tried building the circuit the IC blew after some time, I blew 4 ICs in the course. It might be happening because of the capacitor discharge entering the circuit. Somehow it seems the IC side needs to be isolated from the secondary side of the transformer.
I’ll try to fix this soon and update it for you.
However, when I had tried this 4 years ago that time everything had worked smoothly without any problems, I can’t remember what was the change that allowed this to happen?
Hi Swag.
First off may I congratulate you on your practical designs and you dedication to responding to readers’ questions.
In my own case I hope to build two of your dc cdi units.
I have a Honda 750 twin spark twin cylinder motorbike so I assume I’ll need two units.
Also, can I split the output to two coils or should I put in some isolation circuitry to feed each spark coil? Thanks and regards. Joe
Thanks Joe, I am glad you liked my work.
Regarding your questions, if your two units are designed to work with two different input signals with different timings from the pickup coil then splitting may not be a good idea, however if they are supposed to work together, simultaneously, then surely a single circuit can be used for both the units.
Thanks for your quick response Swag.
In my case, each circuit fires two sparks for each trigger signal.
Can I just connect two automotive coils in parallel or should they be isolated from each other (on separate feeds)?
Thanks and regards
Joe
Thanks Joe, if the timing of the triggers are identical then a single coil output can be bifurcated into two, however if the timing of the two triggers are required to be different then separate coils would become mandatory.
Thanks Swag. Appreciate your help, thanks!
Hi Swagatam, how do you adjust the timing coming from pickup?
Somehow i prefer not to do any mod on my bike magneto, so i still can use the original CDI
Planned to use this for emergency only.
Thanks
Hi Althaf, it cannot be done in this circuit, and manual adjustment is anyway not recommended, because that can cause inefficient operation of the engine.
All my local mechanics would just grind the (thing that activate pickup coil ? we call it “Bulge”, I dont know the name in english, sorry) then moving it to suitable position and then re-weld it, so that 1 to 2 type of CDI that is available in market would be usable for all type of bike here, regardless of different timing implemented on each bike.
But as I stated above, I prefer not to “grind” the magneto, so if one time my CDI is busted,(which happened long time ago) I could pull my handmade CDI, install it, continue in my way, and when I got home, I’m just swap it to the new one.
Thanks for the reply tho, will look up to your other interesting projects.
Cheers
OK understood, however the above circuit has no such feature which can adapt different switching rates as per user preference.
thanks for your fast response
LED is blinking and IC555 circuit work fine
OK great, please use 1K at the base of the transistor and make sure to connect a 1N4007 diode across the collector emitter of the 2N2222 otherwise it can get quickly damaged from the tafo back emfs…..anode to emitter
Hi boss can you tell me what is the ampere of given transformer
not exactly sure, it could be around 2 amps at the input side.
Dear Swagatam
I constructed this circuit but instead of Tip122 I used 2N2222.
then The circuit didn't work, I have tested all circuit connections,I measured the input voltage to transformer (at 12V side) , It was 0V AC,but I disconnect the transformer ,the measured open circuit voltage equal 19V AV.
Could you explain this issue?
Hi Ahmed,
Something is certainly not correct in your design…first make sure your 555 is generating the required pulses…to check this reduce the frequency to some lower level by increasing the pin6/2 capacitor value to say 10uF and then adjust the pot and check the LED response…it must blink…if that's not happening then your 555 circuit is faulty and needs to be diagnosed
by the way 2N2222 could become hot while switching a 1amp trafo.
thanks for your reply
so could I use any non polar capacitor such as film capacitor
105/400V must be non-polar…you can use any type rated at 400V or above
thanks for your reply
Is it rated 400V AC or DC
you are welcome!
400V is the breakdown voltage limit of the capacitor, any voltage whether DC or AC if it exceeds this limit the capacitor will burn.
Dear Swagatam
sorry but I could find BT 151 and 105/400V could I replace them with any LED and 1uF 250V elect Capacitor?
c
Dear Ahmed, BT151 and the 105 components are the two crucial parts of the circuits and cannot be replaced by anything else
Sorry, but could you provide me links for those component or more details about component
you can check out the datasheet of BT151 for more info, 105/400V is a PPC capacitor equivalent to 1uF/400V
this is very useful,I want to make this circuit could you tell me type of capacitor please?
thank you very much, just copy the parts as indicated in the diagram…the shopkeeper will be able to provide you the correct ones.
I need a circuit with 5 joules output energy So I have some questions
How much power this circuit can provide ?
What is the type of transform?is it a pulse transformer?
what is the number of transistor device?
I have not measured the output power so can't specify that, the transformer is an ordinary 0-12/220V iron core step down tansformer, please click on the diagram to get all the details…
Hiya Swatagam! I'm located in the US, and am attempting to build a CDI to replace a faulty one on my 1978 Honda CB400T Hawk. After reading through the comments, I found what the value of the pot is supposed to be for (could this same CDI design be used for inline 4 cylinder motors as well?), so that question is answered. However, going through the parts list and attempting to locate components has not landed me with much success. The 105uF/250V capacitor, for example, I am having a really hard time finding. The only results I've come up with so far are the size of soda cans (which is impractical for mounting and use on the bike) and rated only for intermittent use in, say, starting an electric motor. Does it *have* to be a 105uF capacitor, or can it be, say, 108uF (I ask because 108uF caps seem to much easier to find on supplier sites like Mouser electronics)? The 0-12V/220V transformer has also proven very difficult to locate. Do you have a supplier that offers these things, by any chance?
Thanks so much for posting the schemata, and for your assistance!
Marcus Cross
Thanks Marcus, you can use the same the design for a 4=stroke motorcycle also, although the CDI coil specs could be different for different models, and can be exchanged as per preference.
105 = 1000000pF = 1000nF = 1uF, and 108 = 1000000000pF = 1000000nF = 1000uF/250V…wow that's huge!!…it can be used in place of 105/250V but could be unnecessarily bulky and costlier…but you can try it out it won't cause any harm.
By the way the "105" is not 105uF…it is short code for identifying a capacitor value universally.
getting a 220V trafo in US could be difficult since your country utilizes 120V for the mains….there's a workaround you can try for acquiring 220V from a 120V transformer, you can use a 0-6V/120V transformer instead and the output will be almost 220V provided the circuit is powered with a 12V