In this post I have explained the making of simple delay timers using very ordinary components like transistors, capacitors and diodes. All these circuits will produce delay ON or delay OFF time intervals at the output for a predetermined period, from a few seconds to many minutes. All the designs are fully adjustable.
Importance of Delay Timers
In many electronic circuit applications a delay of a few seconds or minutes becomes a crucial requirement for ensuring correct operation of the circuit. Without the specified delay the circuit could malfunction or even get damaged.
Let's analyze the various configurations in details.
You may also want to read about IC 555 based delay timers. Recommended for you!
Using a Single Transistor and Push Button
The first circuit diagram shows how a transistors and a few other passive components may be connected for acquiring the intended delay timing outputs.
The transistor has been provided with the usual base resistor for the current limiting functions.
A LED which is used here just indication purposes behaves like the collector load of the circuit.
A capacitor, which is the crucial part of the circuit gets the specific position in the circuit, we can see that it's been placed at the other end of the base resistor and not directly to the base of the transistor.
A push button is used to initiate the circuit.
On depressing the button momentarily, a positive voltage from the supply line enters the base resistor and switches ON the transistor and subsequently the LED.
However in the course of the above action, the capacitor also gets charged fully.
On releasing the push button, though the power to the base gets disconnected, the transistor continues to conduct with the aid of the stored energy in the capacitor which now starts discharging its stored charge via the transistor.
The LED also stays switched ON until the capacitor gets fully discharged.
Te value of the capacitor determines the time delay or for how long the transistor stays in the conducting mode.
Along with the capacitor, the value of the base resistor also plays an important role in determining the timing for which the transistor remains switched ON after the push button is released.
However the circuit using just one transistor will be able to produce time delays which may range only for a few seconds.
By adding one more transistor stage (next figure) the above time delay range can be increased significantly.
The addition of another transistor stage increases the sensitivity of the circuit, which enables the use of larger values of the timing resistor thereby enhancing the time delay range of the circuit.
PCB Design
Video Demonstration
Using a Triac:
The following image shows how the above delay timer circuit may be integrated with a triac and used for toggling a mains AC operated load
The above could be further modified with a self contained power transformerless power supply as shown below:
Without a Push-Button
If the above design is intended to be used without a push button, the same may be implemented as indicated in the following diagram:
The above delay OFF effect without a push button can be further improved by using two NPN transistor, and by using the capacitor across base/ground of the left NPN
The following circuit shows how the associated push button may be rendered inactive as soon as it's pressed and while the delay timer is in the activated state.
During this time any further pressing of the push button has no impact on the timer as long as the output is active or until the timer has finished its delay operation.
Delay from an External Trigger
Problem asked by Mr. Glen (one of the dedicated readers of this blog):
I have a situation where I have a pulse of 12V that lasts about 4 seconds (from a rotary switch being turned by a slow motor) but I only want about half a second pulse (to trigger a mechanical bell/chime).
Is there any way to take a long pulse into a circuit and send a much shorter pulse out?
The solution to the above problem is provided in the following schematic:
Two Step Sequential Timer
The above circuit can be modified to produce a two step sequential delay generator. This circuit was requested by one of the avid readers of this blog, Mr.Marco.
A simple delay OFF alarm circuit is shown in the following diagram.
The circuit was requested by Dmats.
The following circuit was requested by Fastshack3
Delay Timer with Relay
"I am looking to build a circuit that would control an output relay. This would be done in 12V and the sequence will be initiated by a manual switch.
I will need an adjustable time delay (possibly displayed time) after the switch is released, then the output would go on for an adjustable time (also possibly displayed) before shutting off.
The sequence would not restart until the button was pressed and released again.
The time after the button release would be from 250 milliseconds to 5 seconds. The "on" time for the output to turn on the relay would be from 500 milliseconds to 30 seconds. Let me know if you can offer any insight. Thanks!"
So far we have learned how to make simple delay OFF timers now let us see how we can build a simple delay ON timer circuit which allows the connected load at the output to be switched ON with some predetermined delay after power switch ON.
The explained circuit can be used for all applications which calls for an initial delay ON feature for the connected load after the mains power is switched ON.
Delay ON Timer Circuit Working Details
The shown diagram is pretty straightforward yet provides the necessary actions very impressively, moreover the delay period is variable making the set up extremely useful for the proposed applications.
The functioning can be understood with the following points:
Assuming the load which requires the delay ON action being connected across the relay contacts, when power is switched ON, the 12V DC passes via R2 but is unable to reach the base of T1 because initially, C2 acts as a short across ground.
The voltage thus passes through R2, gets dropped to relevant limits and starts charging C2.
Once C2 charges up to a level which develops a potential of 0.3 to 0.6V (+ zener voltage) at the base of T1, T1 is instantly switched ON, toggling T2, and the relay subsequently....finally the load gets switched ON too.
The above process induces the required delay for switching ON the load.
The delay period may be set by appropriately selecting the values of R2 and C2.
R1 ensures that C2 quickly discharges through it so that the circuit attains the stand by position as soon as possible.
D3 blocks the charge from reaching the base of T1.
Parts List
R1 = 100K (Resistor for Discharging C2 when circuit is switched OFF))
R2 = 330K (Timing Resistor)
R3= 10K
R4 = 10K
D1 = 3V zener diode (Optional, could be replaced with a wire link)
D2 = 1N4007
D3 = 1N4148
T1 = BC547
T2 = BC557
C2 = 33uF/25V (Timing Capacitor)
Relay = SPDT, 12V/400 Ohms
PCB Design
Application Note
I have explained how the above delay ON timer circuit becomes applicable for solving the following presented issue by one of the keen followers of this blog, Mr. Nishant.
Circuit Problem:
Hello Sir,
I have a 1KVA automatic voltage stabilizer.It has one defect that when it is switched on, very high voltage is outputted for about 1.5s (therefore cfls and bulb got fused frequently) after that the voltage becomes OK.
I have opened the stabilizer it consist of an auto-transformer,4 24V relay each relay connected to a separate circuit(each consisting of
10K preset,BC547,zener diode,BDX53BFP npn darlington pair transistor IC,220uF/63v capacitor,100uF/40V capacitor ,4 diodes and some resistors).
These circuits are powered by a step down transformer and output of these circuit are taken across corresponding 100uF/40V capacitor and fed to corresponding relay.What to do in order to tackle the problem.please help me.Hand drawn circuit diagram is attached.
Solving the Circuit Problem
The problem in the above circuit might be due to two reasons: one of the relays is switching ON momentarily connecting the wrong contacts with the output, or one of the responsible relays is settling down with the correct voltages a little while after power switch ON.
Since there are more than one relay, tracing out the fault and correcting it can be a bit tedious......the circuit of a delay ON timer explained in the above article could be actually very effective for the discussed purpose.
The connections are rather simple.
Using a 7812 IC, the delay timer can be powered from the existing 24V supply of the stabilizer.
Next, the delay relay N/O contacts may be wired in series with the stabilizer output socket wiring.
The above wiring would instantly take care of the issues as now the output would switch after some time during power witch ONs, allowing enough time for the internal relays to settle down with the correct voltages across their output contacts.
Feedback from Mr. Bill
Hi Swagatam,
I stumbled across your page doing research on the web to make my delay more consistent.Some back ground information first.
I am a bracket drag racer and launch the car on first sight of the 3rd amber bulb as the christmas tree is coming down.
I use a transbrake switch that is depressed to lock the automatic transmission in forward and reverse at the same time.
This allows you to rev up the engine to build power for launch. When the button is released the transmission comes out of reverse and moves the car forward under high rpm.
This is like popping the clutch on a manual transmission car, anyway my car reacts to quickly and the result is a redlight, leaving to early, and you lose the race.
In dragracing your reaction time on the launch is everything and it is a game of hundreths-thousanths with the big boys, so I have put the transbrake switch on a relay and put a 1100uf cap combo across the relay to delay its release.
Because of the car electronics I don't believe there is a precise voltage charging this cap every time I activate this circuit and precision is key so I bought a power stabilizer off of Ebay that takes 8-15 volts in and gives a consistent 12volts out.
This turned my season around but i believe this circuit could be made to be more precise and to vary the delay time in an easier way rather than swap cap combos.
Also should I run a diode in front of the relay, not currently because all that is there is the on off switch- where will the current go? I am not an electrical engineer by any means but do have some knowledge from trouble shooting high end audio for many years.
Would love your thoughts- thankyou
Bill Korecky
Analyzing and Solving the Circuit
Hi Bill,
I have attached the schematic of an adjustable delay circuit, please check it out. You can use it for the mentioned purpose.
The 100K preset can used and adjusted for acquiring precise short delay periods as per your specifications.
However, please note that, the supply voltage will need to be minimum 11V, for the 12V relay to operate correctly, if this is not fulfilled then the circuit might malfunction.
Regards.
Simple 5 to 20 Minute Delay Timer
The following section discusses a simple 5 to 20 minute delay timer circuit for a specific industrial application.
The idea was requested by Mr. Jonathan.
Technical Requirements
While trying to figure out a solution to my problem on google, I came across your above posting.
I'm trying to figure out how to build a better Sous Vide controller. The main problem is that my water bath has a very high hysteresis, and when heating from colder temperatures will overshoot about 7 degrees from the temperature at which power is terminated.
It is also very well insulated, with a gap between the inner and outer vessel which makes it act like a thermos jar, because of this it takes a very long time to decline from any excess temperature. My PID controller has an SSR control output and a relay alarm output.
The alarm can be programmed as a below limit alarm with an offset from the set-point. I can use a five volt supply I already have for my circulation motor to run through the alarm relay and drive the same SSR the control output is driving.
To be on the safe side and protect the PID controller I'll add a diode to both the alarm voltage and the control voltage to prevent one output from feeding back into the other.
I'll then set the alarm to stay on until the temperature rises above the set-point minus 7 degrees. This will allow the PID tuning to be adjusted without having to account for the initial temperature ramp-up.
Because I know that last few degrees will be achieved without any power input, I'd really like a way to delay any recognition of the control signal for about five minutes after the alarm shuts off, as it will still be calling for heat.
This is the part I've yet to figure out the circuitry for. I’m thinking of a normally closed relay in series with the control output, which is held open by the alarm signal.
When the alarm signal is terminated, I need a delay on the order of five minutes before the relay returns to its ‘off’ normally closed state.
I would appreciate help with the delayed off portion of the relay circuit. I like the simplicity of the initial designs on the page, but I get the impression they wouldn’t handle anywhere near five minutes.
Thank you,
Jonathan Lundquist
The Circuit Design
The following circuit design of a simple 5 to 20 minute delay timer circuit can be suitably applied for the above specified application.
The circuit employs the IC4049 for the required NOT gates which are configured as voltage comparators.
The 5 gates in parallel form the sensing section and provides the required time delay trigger to the subsequent buffer and the relay driver stages.
The control input is acquired from the alarm output as indicated in the above description. This input becomes the switching voltage for the proposed timer circuit.
On receiving this trigger, the input of the 5 NOT gates are initially held at logic zero because the capacitor grounds the initial trigger via the 2m2 pot.
Depending upon the 2m2 setting, the capacitor starts charging up and the moment the voltage across the capacitor reaches a recognizable value, the NOT gates revert their output to logic low, which is translated as a logic high at the output of the right single NOT gate.
This instantly triggers the connected transistor and the relay for the required delay output across the relay contacts.
The 2M2 pot may be adjusted for determining the required delays.
Sabri says
hi.
I want to control an electric motor with a relay.
I want the relay to close 5 seconds later when the current to the relay coil is cut off.Can you help me with this?
Thank you for everything
Swagatam says
Hi, you can try the 2nd circuit from the above article. Replace the LED/resistor with your relay, and make sure to add a freewheeling diode across the relay coil…Adjust the 2M2 and the 1000uF values to get the desired 5 second delay-off time.
Gajendra says
Hi Swagatam,
I have come across your blog and love it as I have been an enthusiast for long. I don’t design electronics.
I’m making a battery powered drone. I would like to have an on-off control which can be controlled with a tac push button. A 3 second contact to power on the electeonics and 3 seconds press to turn it off.
The current in drone circuit is very high, about 60 amps. Unable to find the solution as weight and space are critical on this small drone.
Should this be software controlled? Can you please help?
Swagatam says
Thank you Gajendra, for your question!
The circuit can be perhaps designed using a 4017 IC and a 555 IC.
Just wanted to know, is the ON/OFF operations done with a single tact switch?
And, what happens if the switch is not released after 3 seconds, and remains pressed for more 3 seconds?
Kindly clarify the above, I will try to help!
Wali says
Hello,
So, I have an application where I am using a D-type flip-flop to toggle my load using a pushbutton. I want to add a trip functionality, so when a trip signal comes, after 5 seconds will the load be turned off. If the trip signal goes out before 5 seconds, the load stays on. If it goes out after 5 seconds, the load will turn on again.
Swagatam says
Please explain the delay trigger operation with more details, I may try to solve it.
Wali says
So the circuit that starts with the output being high when you power it on. Now, when you give it a high signal through the dry contact input, it waits for 5 seconds. If the input stays high for the whole 5 seconds, the output switches to low. But if the input goes low before the 5 seconds are up, the timer resets, and the output stays high. Once the output goes low after the 5-second delay, it stays low as long as the input is high. And when the input finally goes low, the output immediately goes back to being high.
Swagatam says
Ok, you can try this circuit:
https://www.homemade-circuits.com/wp-content/uploads/2024/07/customized-timer-using-nand-gate.jpg
Colin Redway says
Hi Bill
I am a newcomer to your sight as you must realise and i find the content very handy and informative. However i have a situation that i hope you may be able to resolve. I need to be able to identify when a battery source of 12v dc (li iron sealed) drops its voltage to about 10.5 v and triggers a 3 second (approx.) timer to operate a small solenoid. The solenoid will still operate at this voltage. I would prefer to be able to do it without a relay. The trigger as well must only be able to operate once so as not to keep the solenoid on. The system will reset again after the battery is recharge. I am a retired electrician which makes me dangerous in this field so please understand my ignorance in these matters. I have always had a yen to get into this field as a hobby and now have the chance. Hope you can help. Regards Col R
Swagatam says
Hi Colin,
I will try to figure out the circuit soon, and let you know.
If you have any further questions please feel free to ask…
Colin Redway says
Thanks Bill
Swagatam says
Hi again,
Here’s the circuit you can try, it should hopefully fulfil your requirement:
https://www.homemade-circuits.com/wp-content/uploads/2024/04/low-battery-solenoid-activator-circuit.jpg
Colin Redway says
Hi Bill Thanks for replying so quickly. Could you advise me of the value of RX and CX in the circuit you supplied. Regards Col R
Swagatam says
RX can be around 33k and CX can be around 100uF, for getting an ON time pulse of 3 seconds.
Colin Redway says
Thank you
Vikas Mahindra says
Hi Swag,
I forgot to add one additional query for self contained power transformerless power supply circuit. It seems to be good for single application. But can certain modifications be made in circuit to place it just after electric meter? This will help in bypassing sudden surge during power supply in case of power failure.
Swagatam says
Hi Vikas,
Yes, that’s possible if you are able to configure the wiring correctly.
You can configure the following circuit which will ensure safety from sudden power ON surge.
https://www.homemade-circuits.com/wp-content/uploads/2023/01/refrigerator-protector-circuit-with-triac-timer.jpg
Vikas Mahindra says
Very nice site for electronics guys. I was going through self contained power transformerless power supply circuit and was fascinated by its simplicity without using transformer at all. Moreover, triac in circuit seems to be more effective and efficient than relay. But how to modify this circuit for mains supply to automatically turn on after a pre-defined period (say of 5-15 seconds) without the use of push button?
Swagatam says
Thank you Vikas, Glad you liked the site.
For a delay ON, mains operated circuit, you can refer to the first circuit from the following link:
https://www.homemade-circuits.com/simple-refrigerator-protector-circuit/
Saul says
Hi Swag
Many times your schematics have helped me but this time I cant cope myself. Imagine yarn winding mashine that has yarn tension motitoring via simpokle push button. Yarn stuck = machine stop. Problem is that any vibration of thicker yarn causes multiple false and unnecessary stops. My idea is that signal from button is transmitted only if it lasts more that say 0.5sec. Implementing microprocessor seems overkill to me.
One pole of switch is grounded and machine runs on 60v DC.
Do you thing any of your schematics will do ?
Swagatam says
Hi Saul,
What type of switch are you using, is it a manual push button? in that case you may have to replace it with a relay operated switch to implement the switch debounce..
Saul says
Yes simple micro switch is beeing used. It shorts some microcontroller input to ground to stop machine. I think transistor or mosfet will doo. Switch should trigger timer instead of what it did before. Does it have sense ?
Swagatam says
OK, you can implement the following setup:
Take a BC547 transistor.
Connect the collector to the microcontroller input.
Connect the emitter to ground.
Connect the base to a 10k resistor.
Connect the other end of the 10k to one terminal of the microswitch, connect the other terminal of the microswitch to the positive line.
Connect a 1uF capacitor between base and ground.
Saul says
It will work on 60 volt ?
Another question . Do I need resistor to discarge cap in order to not acumulate short burst chargindg ?
Swagatam says
For 60v you can use BC639 bjt. To ensure proper discharge of the capacitor you can connect a 2.2k resistor parallel to the capacitor.
Saul says
Thanks a lot.
Your advices are very helpfull.
Swagatam says
Glad to help!
Hefni says
Kindly I ask you what is 2m2 in the circuit best regards
Swagatam says
2M2 = 2.2 meg ohm resistor.
Dean G says
Is the PCB shown in the Delay ON Timer Circuit Working Details section available for sale?
Swagatam says
Sorry, we don’t make PCBs now, so I may not be able to provide it to you, nevertheless you can easily get it done from any local PCB designer in your area. These PCB designs were not created by me rather purchased from an external source so please double check it before manufacturing.
Fabio says
Hi Sir,
My name is Fabio. I saw all your project but I need one with small modification if you can help please.
I need a Power ON Delay with 3 channel output controlling a MOSFET not a relay.
When power is applied the first channel wait 30s before come ON. The second channel will wait 60s after the first channel is ON, and the third channel wait 60s after the second channel is powered ON.
The time in “s” doesn’t need precise.
Hope you can help with this project.
Thanks
Swagatam says
Hi Fabio,
I think the second concept from the following article will work for you. You will have to configure a MOSFET with the collectors of the BC557 transistors.
https://www.homemade-circuits.com/cube-light-circuits/
Tim says
Hi Swagatam, i have a question on the timers, i understand and have a grip on the single use sw from a transistor, however i need to stop an 74LS90 which is a single pulse/dragdown command then i need a second pulse/dragdown to reset the 74LS90. i am not sure it would work with a single pulse/dragdown from a single transistor to do both operations as they would be simultanious and atthe same time, do you have any ideas.
Swagatam says
Hi Tim, I haven’t studied the 74LS90 IC yet so I am finding it difficult to figure out the problem.
Wally Lee says
Hi Swagatam,
Atoto Head Unit A6G2A7PF (2G+32g)
I have installed the above head unit in my diesel Toyota Prado 120 Series.
The glow plugs in the engine take up to 5 seconds to heat after which I can start the car.
In this time my head unit begins to start but then crashes and restarts when I start the car, impacting recently adjusted settings e.g. steering wheel audio settings and who knows what else.
Is there a way to delay the start of the 12v (ignition on) to the unit so that it starts after the car is started?
I hope you can assist.
Wally
Swagatam says
Hi Wally,
You can delay the 12V supply to the ignition circuit through the following circuit. The 12V supply to the ignition can be applied through the N/O relay contacts. The C2 R2 component values decide the delay time after which the relay will operate, once the input 12V to the circuit is switched ON.
https://www.homemade-circuits.com/wp-content/uploads/2022/04/delay-ON-timer.jpg
Pete Mantle says
Hi my name is Pete I have just built a 300 led hex style sci – fi computer display when first turn on all the leds are red and whilst the timers in the devices are running at different rates for the first 2/3 minutes the effect is great after this time the slow change diodes don’t look too impressive . I need a circuit that will will switch on for 2/5 minutes then crash to 0 volts and recycle again at 5 volts for 2/5 minutes before repeating the same be nice if i could actually vary the time with a potentiometer to experiment and gauge the exact best time to gain maximum led colour difference and thus the best decorative effect. Regards Pete Mantle
Swagatam says
Hello Pete, I did not understand what you meant by 2/5 minutes, please clarify!
Pete Mantle says
i meant a variable control time from say 2 minutes to 5 or even 6 minutes i want to be able to vary the time with a pot to experiment for best results i really need the 5volts to collapse pretty fast also in order to reset the leds to red ( the starting colour ) thanks for your swift response
Swagatam says
You can do it with a help of a simple IC 555 flasher, as shown below. The pin#3 will alternately oscillate from positive supply level to 0V level. The ON OFF timings can be adjusted by adjusting the 1M pot and the 22K resistor values. But how will you use the pin#3 to control your LEDs? You will require a BJT or a MOSFET connected at pin#3 to do this:
https://www.homemade-circuits.com/wp-content/uploads/2011/12/f149dbce8308cab5de03978b6d8380ec6ee022f8_orig-1.jpg
Pete Mantle says
to clarify I need t to deliver 5volts which will crash to zero after 2 to 6 minutes then restart AGAIN at 5 volts ( with a pot so I can vary the time interval ) then repeat the whole cycle again constantly. also need the voltage to completely hit zero in order to start the colour change leds at red .
Francesco Fusco says
Hi. Your blog is very great. Please, can I explain my need? I was searching for a circuit that when in input receives a signal of 12V AC, whait for 30 seconds and after then send a 5VDC pulse to a relay. The delay and the activation time should be configurable. Thanks a lot.
Swagatam says
Hi, thanks for liking the blog! You can try the following circuit. Your 12V will need to be converted to 12V Dc first. For providing 5V to the relay disconnect the emitter of the T2 BC557 and the connect this emitter with a 5V DC. Make sure to connect the ground of the 5V DC with the circuit ground:
https://www.homemade-circuits.com/wp-content/uploads/2021/03/double-delay-circuit-compressed.jpg
T1 can be BC547 transistor.
R2 and C2 can be altered for adjusting the delay range
vespucci says
I need a simple solution for giving a little delayed impuls to a relay.
I already have the circuit which makes a short impulse out of the steady 12v connection.
1000uF in parallel to 10 Kohm on the negative input do the trick. Now I only need to happen this impulse (or the supply to this part of circuit) about one sec delayed. Time does not need to be exact.
I tried nearly all of your delay circuits but nothing worked;-(
My relay coil has 1kohm.
My favorite would be another rc circuit.
Can somebody please give me a hint how to combine those 2?
Thanks, VESPUCCI
Swagatam says
All the above circuits are tested and are working. The above circuits are not for a single common application but have different applications. You cannot use all the above circuits for a single application, they won’t work. They all have different specific functions. You have to understand them and then apply.
To understand your application I will need the schematic of your diagram, without a schematic it may not be possible to find a solution.
vespucci says
https://www.homemade-circuits.com/wp-content/uploads/2023/04/RelayMomDelay.jpg
Swagatam says
Please try the following circuit:
https://www.homemade-circuits.com/wp-content/uploads/2023/04/transistor-relay-delay-circuit.jpg
vespucci says
I tried with C945 transistor. But unfortunately not working;-(
No delay in powering. Very little delay after dividing.
Swagatam says
It has to work, because it is a tested design, it is just about adjusting the resistors and their values.
Try the following modified circuit:
https://www.homemade-circuits.com/wp-content/uploads/2023/04/BC547-relay-delay-circuit.jpg
Eric Crigler says
Good evening, I’m working on a project that will require a 12V circuit board to control a 12V solenoid. It seems basic and assumed i would be able to find this board with out much trouble but so far ive proven myself wrong. I need the circuit board to switch on my solenoid for 3-5 seconds ( i dont know exactly yet) one time every 30 days. Obviously the 30 day delay is the hurdle I’m encountering Could you get me on track to building this board?
Swagatam says
Hi, the 30 delay can be solved with a day/night light detector, which will detect the passing of each day with the help of the day/night light source. This day night pulse can be then converted into 30 day counting using 4017 IC, and subsequently at the final stage a 3 second delay timer can be added for activating the solenoid.
Eric Crigler says
Thank you for the quick reply. The day/night detector would absolutely work but I left out a detail. My mistake. The device for this project will be 100% indoors and set up either in a closet or the attic. I won’t be able to wire in any kind of external day/night type device, I would need it to all be integrated in a standalone circuit board with a 12V power supply. Thank you again for your input
Swagatam says
Oh, in that case in can be difficult for me to figure out an appropriate circuit design for you, because 30 day is a long delay and making a 30 day timer without errors can be quite difficult.
Joseph says
Hi Mr Swagatam
Re: Dumbwaiter startup problem.
This is some Chinese unit installed by some previous owner which has no manufacture ID and no papers or circuit information.
Each of the two floor levers have a power on/off switch and an up and down push buttons that light up just after the power is turned on.
The 220 V AC geared motor is controlled via a frequency Voltage converter and triggered through a mini plc card which gets its 24V power through the FVC.
If we push the required up or down button, when the buttons light up, too quickly the system fails and we then need to reset, by turning the power off and on again, and then wait for 2 to 3 seconds before we press the required button after it lights up, before the unit works correctly.
We concluded that the FVC, although it outputs 24v to the plc and the button led power, the other part of its function circuit is slower, which is the delay factor.
Other then introducing a time delay in the plc to delay the start up, which we have no information on, we would like to introduce a delay to the 24V power outlet from the FVC to the PLC, of 3 seconds in the simplest, cheapest, reliable way.
Do you have a simply circuit for me please.
Swagatam says
Hi Joseph,
You can add the following delay based LM338 power supply to your existing power supply:
https://www.homemade-circuits.com/wp-content/uploads/2012/04/LM338slowturnONpowersupplycircuit-1.png
You can adjust R1/R2 to change the output voltage and adjust R3/C1 to change the delay to the desired levels.
Dale Warner says
Hi Swagatam.
I’ve looking through google & ebay thinking that what I’m looking for should be easy to buy made but not turning out so easy. There are a lot of relays that delay power on, or turn power off after a set time, but the supply power needs to be on. What I’m after is a device that once my ignition is turned off, a relay stays open for a set amount of time so that I can hook one up to my electric windows & another to the cooling fan under my intercooler.
I did buy one off ebay & thought maybe the cap on it & adjustable pot would be enough to hold the relay open & direct power to the relay would stay on the load for a few seconds for windows, minutes for fan.
Cheers
Dale
Swagatam says
Hi Dale,
I think you should try the following circuit, it might be exactly what your are looking for.
https://www.homemade-circuits.com/wp-content/uploads/2022/12/delay-ON-timer-for-car-windows.jpg
achy1243 says
Great work , I needed help on, how to do the manual calculations, for the *With push button Delay timer*, circuit
Swagatam says
Thank you, unfortunately I do not have the formula for calculating the RC time constants.