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Good morning Swagatam,
My name is Dorian, I am in need of some assistance with building two AC supply sources. I have a darkroom, I use an Omega Super Dichro enlarger. There are three different output voltages 120Vac, 6.3 Vac and 39.4 V ac. I would prefer the option to build two supplies that are variable to adjust for the 6.3 and 39.4. The transformer power supply, (Omega Chromacontrol) which includes the timer is severely arcing. I would like to have the transformer rebuilt, I can not find a source. I decided to take a different approach. I do not need the timer. I need to supply the enlarger head with the above mentioned voltages (measured at the supply). No where can I find schematics for building AC to AC. Just for information, I have a degree in Electrical Engineering, spent 30 years in avionics, I have lab experience. Much appreciated.
Good Morning Dorian,
Instead of trying to design an AC-to-AC electronic converter, I would recommend the simpler way to use two separate transformers, because that usually stays more reliable and there is less trouble later.
For Supply 1, which is for 6.3 Vac adjustable, we can use a transformer with 120 Vac on the primary side, then the secondary can be 6 Vac or 7.5 Vac, depending on what is available.
Power rating can be around 1 A and if the lamp current is not known higher, then this usually remains enough.
If exact 6.3 Vac is needed then we can add a small series resistor or maybe trim it a little through a variac, to bring it closer.
Now for Supply 2, which is 39.4 Vac adjustable, again primary stays 120 Vac but secondary can be 36 Vac with some trim adjustment, or directly 40 Vac if that type is available.
Power rating here depends fully on enlarger lamp current, so unless that current is known, then exact transformer size can not be fixed.
Since 39.4 Vac is not a common value, then easiest way is usually 36 Vac transformer with a small buck or boost trim winding.
Or we can use two secondaries, 24 Vac and 15 Vac and connect them in series.
That gives 24 + 15 = 39 Vac, so now it comes very near the required value.
Hello from Italy, Swagatam!
For my motorbike I would need two circuits i’m unable to find anywhere… maybe I’m missing the right keywords, but right now I have no solution.
1) I would need a 12V stabilizer: i’ve put LED lamps on my bike, and also a DRL light, but they filckers a lot (the less power the bike uses -it has heated handgrip and seat- the more they flickers). So a Motorbike/Car 12V stabilizer, able to handle the power for two low/high beam LED lamps could be very useful.
2) on the Kawasaki of my son there’s such device, so his lamps go ON only when the engine is running, not just with the key switch.
Here’s the schematic: https://imgur.com/yQL2XCu
and here the detail: https://imgur.com/IF1vyWz
I don’t understand how it works, but I could use a relay that goes on only after the engine runs (maybe even delayed by a pair of second) so I could power some circuit not just by turning the key.
Thanks!
Hi Parduz,
for the stabilizer circuit I would recommend using a boost converter circuit such as the following one:
https://www.homemade-circuits.com/xl3608-5v-9v12v-dc-2-amp-boost-converter-module/
Make sure to put a large capacitor such as 6800uF/50V across the output terminals of the converter…
For the kawasaki bike, you can try adding the following relay circuit, and check how it works:
https://www.homemade-circuits.com/wp-content/uploads/2026/03/ignition-relay.jpg
Thanks.
About 2) I’ve drawed it in the Circuit Simulator:
https://imgur.com/a/P9bfG7e
Have I understood you well?
How can the relay retains itself once it switch on? To avoid fast switching if the engine have problem starting or chokes?
Your diagram is correct.
However, the relay will not remain latched in this diagram, if the engine stops or halts.
If you want the relay to remain latched, you will need to replace the BC547 transistor with an SCR C106.
BC547 base will replace with SCR gate, collector with anode, and emitter with cathode.
I previously found this power supply design on homemade-circuits.com.
I do not see it on the site any longer.
I do not remember the output specs.
I need something similar using the 2n3055 that will output up to 50vdc 10amp with overcurrent protection with led and audible warning.
Thanks for your interest, It is still there, here’s the article link:
https://www.homemade-circuits.com/0-to-50v-0-to10amp-variable-dual-power/
i need your help with 3000kw sinewave inverter here it’s failing
Please give more information…
Hi, Swagatam,
There are light sensing circuit and darkness sensing circuits using LDR all over the internet.
Is there a schematic on your site when both of them combined together?
Idea behind it is: when light level drops below predetermined level – LED comes on ( saying “Too dark”) , when light level gets above certain level – another LED comes on (saying “Too bright”). Levels could be adjusted with 2 different potentiometers, to have some hysteresis.
Do you ever come across such a schematic? It could be a good idea for your next tutorial.
Best regards, Michael
Hi Michael,
I think you can customize the circuit explained in the following article.
https://www.homemade-circuits.com/how-to-build-dual-solar-tracker-system/
You can eliminate the transistor bridge stage and connect the LEDs directly from the opamp output to ground with 1k series resistors…
Thank you, Swagatam,
I will look into the schematic. Want to have just one LDR and LM339 as a comparator.
https://www.homemade-circuits.com/how-to-make-ic-lm339-circuits/
Best regards, Michael
Yes, actually it can be designed using a single LDR and two comparators….let me know if you need any further help!!
Hi,
Re:Simple Function Generator Circuit using IC 556
According to the diagram IC 556 is showing with 8 pins however IC NE556 has 14 pins.
Thank you
Hey Walter, can you please comment under that same article, then I will be able to quickly refer to the diagram and answer your question…
Hey Swagatam, thank you for quick response. Diagram: Simple Function Generator circuit using IC 556 on the diagram is showing IC1 556 and power supply is applied to the pin 8 – + 9V.. According to Digi-Key and NTE INC CROSS REFERENCE IC NE556 has 14 pins and the power supply is applying to the pin 14 not 8. Because IC 556 doesn’t exist with 8 pins. Thank you.
OK thanks got it, that IC is supposed to be the IC 566 and not IC 556 as mistakenly shown in the article…
however I have now replaced it with the following diagram using IC 555….which makes more sense now:
https://www.homemade-circuits.com/wp-content/uploads/2020/04/555-function-generator.jpg
Thank you Swagatam, 555 timer makes more sense. Have a great day. Walter
You are welcome Walter, have a great weekend… let me know if you have any issues with the circuit…
Swagatam DA,
Can we make an AC energy saver like Airtron. https://greenco.in/casestudy/Technical%20Bulletin%20No%205%20%20-%20Energy%20Savers%20For%20Air%20Conditioners%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20.pdf
The unit is very expensive. we can make it easily with Arduino and a temperature sensor. That will affordable for everyone. Please check the scope.
Thanks Abhirup,
It looks interesting but we do not know about the algorithm….if possible I will try to crack it and let you know…
Hi Swagatam. I’ve been following you for many years. I have two water pump motors, and a second one as a spare. They are activated by a pressure switch. I want them to operate sequentially each time a signal comes from the pressure switch. This way, both motors will wear out equally. Do you have any circuit recommendations? Thank you very much.
Thank you Ismail,
I guess you want to operate the motors alternately so that they share the load operation equally, and both the motors get prolonged life, and wear out uniformly.
In that case I think you can try the following concept:
https://www.homemade-circuits.com/alternate-switching-relay-timer-circuit/
For triggering the circuit through a pressure switch, you can connect an SCR between the positive terminal and the pin#4 of the IC, with pin#4 also connected to ground through a 10k resistor.
Next, the gate of the SCR can be configured to sense the trigger voltage through a suitable resistive divider network.
Sorry, I think I misinterpreted the question, the above concept will toggle the motors continuously on each triggering, which is not good….you want the motors to toggle sequentially, for alternate sensor triggering. In that case, the following 4017 IC would be a better option.
I built the circuit, but it didn’t work. I can’t see any voltage across the 10k resistor on pin 14. What voltage is required for triggering?
That means the voltage from your pressure sensor is too small, you need minimum 5V at pin#14….. please check it separately and let me know how much voltage are you getting from the pressure sensor output…then I will suggest the required modifications…
Thank you very much, sir. I will try it as soon as possible. Greetings from Turkey.
You are welcome Ismail….
I replaced the 4017. There’s a gap in the timing belt transitions, as you can see in the video. It would be great if a relay activated with each timing signal.https://youtube.com/shorts/aVRog1_bwaM?si=5pOgRgnvTpT3QUYX
OK Understood! you do not want the switch off action for the motors after each sequence is completed.
In that case please do the following modifications in your existing circuit.
Replace pin#4 connection with pin#3
Replace pin#7 connection with pin#4
Pin#7 can remain open and disconnected.
Hello swagatam,
I’ve been looking at the Korg Volca Nubass and more specifically its supposed “vacuum tube VCO”. This really intrigues me but I was unable to find any available schematics or information on how this was done and I was wondering if you knew. Thank you!
Hi Emerson,
actually this “vacuum tube VCO” thing in Volca Nubass is not like those big old glass tubes we see in vintage synths or guitar amps, not that type. Korg Volca Nubass is using this small thing called Nutube, it is actually a real vacuum tube only but very tiny and low power, so it can run inside this small Volca box without heating or high voltage drama.
Now the company never released schematics, so nobody outside really knows the exact circuit but from what Korg itself says and from people who opened it, the tube is sitting in the oscillator sound path and also in the sub bass and drive part. So the oscillator is analog but the Nutube is there to add that tube like uneven harmonic feeling, not some fake digital effect.
So yes, it is a real vacuum tube, but done in modern style, not old school tube VCO like 1970 lab equipment, more like clever compact tube flavor added into an analog synth.
That’s so cool thanks for sharing.
Thanks, glad you liked it….
Hey Swagatam, I’m a big fan of your website and your audio circuits.I was wondering if you could help me out with a project Idea I have. I’m trying to make an analog pitch shifter guitar pedal with two pots. One pot goes from an octave lower than the sound source to an octave higher than the sound source, and the second is the ability to blend the original signal and the modulated signal. I’m not sure doable this is but I thought I’d reach out anyway in case you were able to make a schematic for this. Thank you!
Hey Emerson, thank you very much for liking my website and audio circuits.
About your idea, I must say that proper analog pitch shifter which can smoothly go from one octave down to one octave up using a pot, is not really possible with simple analog circuits. Pitch shifting needs time stretching and compressing of the signal which is why most good pitch shifters are digital.
With analog circuits, we can do octave down and octave up effects separately, using rectifiers, dividers or bucket brigade ICs but the sound will be rough, noisy and the range will be limited. Clean sweeping pitch control like modern pedals is not feasible using pure analog.
The blend control part is easy, we can mix original signal and effected signal using an op amp and a pot.
However, minus one octave to plus one octave with analog pots is not practical.
Thank you for the reply! I understand that this is likely not possible, but would a circuit that’s fixed at say a fifth (the music interval) be possible? I built your robot voice modulator and it seemed to have pretty defined fifth harmonics.
Yes now this is more doable, because fixed intervals like a fifth can be made with analog tricks. What you can do is use full-wave rectifiers, frequency dividers, and mixing to create harmonics at a specific interval. Like in my robot voice modulator, the circuit creates extra harmonics and when you mix them with the original signal, you get a defined interval effect, for example a fifth.
Hi Swagatam,
I’ve noticed that in your health related circuits the “Blood electrification unit” from Bob Beck isn’t included.
I think you will be interested.
But if you share this circuit, It is very important that the protocol is also followed. The effects of i.e. medical drugs can get 10x stronger during the electrification process.
I think the importance of this Device stands in one line with such like Joule Thief or Bedini SSG
Thank you so much Waldemar, for this interesting suggestion…
I will definitely investigate this concept, and if it is feasible i will include this concept on my website.
Many thanks again.
Dear Swagatham
I am looking for PCB kit for 1000Watt amplifier you published, do you know where can i get that kit ordered, Thanks.
Thank you Swagtham truly appreciate your response.
You are welcome Suresh!
Dear Suresh,
PCB kit may not be available readymade, you may have to contact a PCB manufacturer and get it fabricated for you. There are many PCB designers online whom you can contact and check who offers the most reasonable price.
sir how are you home was work
I have driver board circuit sg3525 lm 358
which is do ups transformer or ferried core transformer
which MOSFET is quality for power
please I need diagram for this circuit inverter circuit
Abdulkarim,
You can use UPS transformer or ferrite transformer as you like by adjusting the operating voltage, PWM etc of the circuit accordingly..
MOSFET will depend on the battery, load, transformer specifications…
Sure, please send the details, if possible I will try to help!
Hello, thank you for the information. I am doing home appliance board repair. I am thinking of a circuit to test an air conditioner compressor. I want to drive the IGBT module directly. I have such an idea. If you want to help, I can send the detailed module. I would be happy if you can assist. Our Turkey will advance and develop. Regards.
No Problems David, all the best to you, and let me know if you have any issues with the circuit…