Help needed with circuit design


Please help me with this circuit design. I would like to use 3 (or more solenoids) with 48 Volts current. I assume that this circuit divides 48 Volts to three 16 Volts amount for each solenoid.

The Arduino is needed to put each solenoid on one by one in a loop.

My actual question is that is this circuit correctly designed? If not how would you change it? If I switch 48 V power on will it blow my arduino to thousand pieces? And so on. All help prechuated and thanks in adcance.


  1. What is the operating voltage of the solenoids?


  1. If they are 16VDC Solenoids, you don't add voltage when adding a solenoid, it would simply draw higher current(amperes).

Example: If you have a solenoid that draws 10mA at 16 volts. Two of them together would draw 20mA at 16 volts. Three would draw 30mA at 16 volts... so forth...

  1. I am assuming at least three of the diodes pictured are "flyback" diodes. If not they are in the wrong polarity. "Flyback" diodes should be wired in parallel to the coil.

  2. The forth diode would only serve to impede your circuit.

I'm sorry to tell you, that i think you have several things wrong.

  • In your circuit, each solenoid will see the full 48V.
  • I believe that the type of transistor is 2_SA1943, not 25_A1943 (letter S, as opposed to number 5).
  • The 48V supply is connected with the wrong polarity.
  • Using PNP transistors, you need to connect the emitters to the +5V, and not GND, so that you can take the base negative with respect to the emitter.
  • You need a much lower value resistor between the Arduino output and the base of the transistor. With the value shown, maximum base current will be around 0.5 mA. From the datasheet, the gain of the transistor can be as low as 35 (p2). I don't know what current the solenoids need to operate, but I think it is likely to be more than an amp, so you will need several 10s of mA of base current, to ensure that there is enough collector current. You probably need a few hundred ohms, not ten kilohms.
  • As noted by puguerra75, the protection diodes are incorrect. You need to have a reverse biased diode connected across each solenoid.

Flip things over - use N-channel MOSFET to sink current from solenoid coil to turn them on.
Part AOI514


Thank you for your adivice. I made a remade sketch of the circuit. I hope its better now.

I think that for my purposes its best to use potentiometer in order to seek for the right voltage for the solenoids. This is a circuit for test purposes you know.

Did you even read the previous posts?

Hi, What is the part number of the solenoid? Can you post a picture of it? Using a potentiometer will not help you.

Before you put anything together you must establish the characteristics of your components. If you post a picture we may be able to help. Do not apply 48V to you arduino, what model arduino is it, UNO, Mega, Due.....?

What is your application that needs these solenoids and are you going to have any input to the arduino to control them?

Tom..... :)

Dear Tom,

Thank you for your help. I try to clarify my project.

  1. My solenoids are selfmade. This is the point of the whole thing. I want to test them and know how much magnetic power I can get from them.

  2. I got an advice from my brother that I should use voltage regulator in order to protect my Arduino UNO unit from total frying and kaboom.

  3. As said my system is Arduino UNO R3. From time to time I use similar Funduino R3 which is a cheaper copy of the Arduino.

  4. Please take a look of my latest drawing. I tried to put the voltage regulator to its right place.

Above is a link to my voltage regulator candidate.

I know very well that 48v is a very high current and almost killing so please be accurate when advicing a newbie. Serious accidents are possible.



RaiRaiRai: Hello,

Please help me with this circuit design. I would like to use 3 (or more solenoids) with 48 Volts current. I assume that this circuit divides 48 Volts to three 16 Volts amount for each solenoid.

this is completly wrong in many ways. you say 48 volts current. what do you mean ? volts is one thing, current is another . volts current is not a thing unless you mean to calculate power. your next statement makes me believe you are not using terms correctly. if you have 48 volts and use 3 devices, you do not get 16 volts. each device will get 48 volts. if you have 100, each will get 48 volts.

if you connect one end of one to 48 volts and the other end to one end of your second one, this is 'series' then each one will see half of the total., if you put 3 in series, then each will see 1/3.....

your schematic shows your transistors between the 48 volts and your coils. can you post a link to the data sheet of the transistors ? used on the high side or higher voltage side of the load (your coil) these needed to be pnp type or p-type and designed for high side. the more common type and lower costs ones are n-type and go on the low side, or between your coil and ground. My friend, I think you are making many assumptions and not using the words correctly. I assume that English is not your native language? if we ( all of us and you ) work together and make sure the basic stuff is correct, your project will be successful. it looks like you have the right parts, we just want to make sure you have them put together correctly.

dave-in-nj: I assume that English is not your native language?

From perfect english: to this: All help prechuated and thanks in adcance. This might be the source of the schematics: Some sort of 3-phase motor with a completely wrong schematic diagram. Leo..

Yo to all!

I am not anykind of troll. ??? However I do not speak English natively. Yes - sorry about my English. Try to speak Finnish then. I think it is almost impossible for most of you.

Furthermore I do not have a formal education of an electric engineer. Yes - I am a hobbyist and on the newbie level what comes to electronics.

So this thing is twice as difficult to me than it is to most of you. I think most of here do not have an artist background and Finnish as a mother tongue. Please be patient! :grinning:

I really would like my system to work. So…Lets continue this until it is a sound circuit.

I mean 48 volts. Yep Volts are Volts and current is measured with amperes. Or something like that.

BTW…I have done this circuit in some form to be functional.

Yes this is TOMGINE motor controller. A wonderful new motor(hopefully :smiling_imp: ) which I have invented. But it is still an amateur invention and I have big difficulties right now with that. I have a reason to believe that it works. It has given me a sign of life. It certainly works as a power generator and it has produced some electric power.

Why I opened the source of the TOMGINE? Because I do not know how make my idea alive as alone. Therefore I wish that this Arduino world would be interested of the Tomgine project. So if somebody makes this engine to work I am really thankful and I wish that it will be developed by much better engineers than I am.

Cheers and have fun with Tomgine. It’s not patented and made for you all.

In the attachment there is latest image of Tomgine. It has 6 solenoids. I am planning to 3D print it when I have money. It may take a while. I think it could work better than 3 solenoids model.

Here is Tomgine in its latest form. Its made from plastic but making this from brass costs several hundreds of Euros. It needs more solenoids, a metallic structure and more electric power in order to work.

I hope developing this interests somebody…

Please look at post #3 from Crossroads, and the attached diagram.
You are doing what is called Highside Switching of your solenoids.
With your circuit configuration the solenoids will be ON all the time.

Tom… :slight_smile:

Ok. Thank you for your advice. However the configuration works in real life but not in this schematic. This leads to a conclusion that it is the schematic what it wrong but not the actual configuration. Please take a look of the video on the page:

and you can see it in a full action. But of course I would like to make a decent good schematic too of the configuration which is possible to read by everybody.

The leds blink as they should but the power which comes out of this configuration is too weak for Tomgine.

Hi, What voltage are you using for the supply to the LEDs, and what is the PCB with the digital display?

If you pause your video I think you will find that you cannot stop on a frame where only one LED is ON and the other OFF. It looks like they dim and brighten and its two LEDs bright and one dull.

Slow the strobe rate down to one step per second and check that you really are only turning ON one LED at a time.

Tom... :)

The PCB with digital display is a Chinese motor controller with a potentiometer.

Also the LEDs do blink as they should. They blink one by one in the order 1,2 and 3 in a loop. Is there a need to proof this? I have seen it by myself when I tweak the speed of the blinking to be slowest possible. I can show you another video where this blinking is slow and desired but maybe this is unnecessary I guess.

The input power for this motor controller is 15 Volts with 4.2 Amperes. However the power which comes out is rather weak for the LEDs. I tried to measure this voltage with an electricity meter but once I do not have an oscilloscope I am not sure whether or not the result what I got is really valid and reliable. Also the LEDs go on and off all the time so the values in this cheap electricity meter of mine jump wildly up and down. However it seems that one LED will get about 4 Volts power when the value is up. But as said I doubt that this figure really means anything. However the LEDs has no resistor in it so the power cannot be really high because the LEDs do not overheat or is too bright or explode. If the power was full 15 Volts and 4.2 amperes I guess that the LEDs should explode one by one without any resistors. I have also tried the 15 Volts and 4.2 Amperes directly without that Chinese motor controller. This did not help in any ways and the power was weak.

So I am thinking that how to get out more power from my circuit? My system is not a really economical system by its power use currently and I do not know the reason why.

Glad your identity and intentions have been cleared.

What you probably need is a 3-phase drive circuit. Three coils, supplied with e.g. 12volt. And three logic mosfets (not transistors) that switch the three coils to ground. With 1N4004 kickback diodes across the coils. Should the three coils should be driven by a modified sine wave (PWM)? Like a 3-phase power circuit. I have seen ESC modules on ebay, but never used them. Maybe two of them for the new motor. A 6-phase drive circuit. This should be easy for an Arduino. Maybe something like that has already been done. Anybody? Leo..

Hi, That motor controller is not a variable power supply, it is a PWM motor speed control. You are not getting a smooth DC voltage out of it, it is Voltage/Current pulses.

Please Research Ohms Law. Research PWM motor speed controls, Research High Side Switching, Research Diodes. Research switching inductors (solenoids).

Are you trying to make a Bedini Motor?

Tom...... :)

Hi to all,

Yes my attempts to make a new kind of motor are sincere and I really want it to be low cost and open source. However I do not think that my motor is exactly a Bedini motor. There is one important difference: The permanent magnets of the motor are bearings as well. This reduces the amount of the needed parts for the motor. But I think there are many other differences too. You know I cannot declare that my idea is free and open source if I am not really the first to publish this kind of motor. So it is important thing that somebody thinks the novelty of my idea too.

However I am really thankful that you mentioned this Bedini motor. At first glance there are maybe similarities but there are also plenty of differences.

I will return to this subject later. The idea of using mosfets is better than transistors only.