[Review] Automatic Gong with 36V Solenoid & Nano 33 iot

Hi

My goal was to build an automatic gong and have a working prototype now. This is my first project and I had almost no prior experience with circuit design. So before converting the prototype into the real build, I'd like to ask if there are obvious problems in the circuit or if there would be room for improvement.

Major Components:

  • Arduino Nano 33 IOT
  • Sparkfun Solenoid - 36v (ROB-10391)
  • DFRobot DC-DC Boost Converter (DFR0123)

Approach:
I'm using a 12V 2A DC Power Supply to power both the Arduino as well as DC-DC Boost Converter. Arduino is used to control the boost converter and the solenoid. I'm using mosfet high side switching to enable the boost converter and mosfet low side switching to trigger the solenoid. The boost converter is boosting to 32V. In order to ring the gong, the arduino first turns on the boost converter, waits 250 ms, then turns on solenoid and after 25ms turns off both boost converter and solenoid.

More details can be found in the attachment (breadboard & schematics). Note: I used DC motor in fritzing as there was no solenoid part. The smaller bread board represents the 12V DC Power Supply

I tried to simulate the circuit, but had not much success. So there was some trial & error involved in choosing the electronic components, that why I still have some questions:

  • Are the resistors between digital pins & gates of transistors necessary?
  • Are the source-gate resistors necessary?
  • Would you use other mosfets / resitors values?
  • Is there a risk to damage nano over time with this circuit (reverse voltage / current)?

Would be great to hear your ideas/advice/comments on the project.
Best regards

  1. Are the resistors between digital pins & gates of transistors necessary?
  2. Are the source-gate resistors necessary?
  3. Would you use other MOSFETs/ resistors values?
  4. Is there a risk to damage nano over time with this circuit (reverse voltage / current)?
  1. Yes, but remove R2
  2. Yes
  3. Don't know, requires too much time to research. Do they work OK? If so they are probably OK.
  4. Not that I can see

I don't see any point to the double switching, just turn on and off the boost converter, unless you tried that and it caused a problem I cannot think of.

If the only thing the boost converter powers is the gong then you can switch its 0V input, no need for high side switching if what I said above about not double switching is OK.

You really should power the Nano from 5V not 12V, the on board regulator is crap. Use a buck converter.

++Karma; // For a nice clear first post with images properly included and clear questions.

TIP120 is a Darlington transistor and unneccesary heavy transitor use for some 10 Amps. As I see a "normal" little NPN transistor would work.

Why not let the Boost Converter run all the time and use a logic MOSFET N-channel switch the 36 volt? 2 resistors and one MOSFET.....

Railroader:
TIP120 is a Darlington transistor and unneccesary heavy transitor use for some 10 Amps. As I see a "normal" little NPN transistor would work.

thanks, is there any downside using unneccesary heavy transitor transitor (apart from higher cost)?

Railroader:
Why not let the Boost Converter run all the time and use a logic MOSFET N-channel switch the 36 volt? 2 resistors and one MOSFET.....

This was my initial version of the circuit, did work fine. But then I wanted to switch the boost converter due to power efficiency.

PerryBebbington:
You really should power the Nano from 5V not 12V, the on board regulator is crap. Use a buck converter.

What that downside when using Nano built in regulator? Will it eventually die?
I try to make everything as simple & small as possible. If I add another converter, I have two converters. With 12V input, then converting down to 3.3/5.0 for nano, and up to 32 V for solenoid. Wouldn't it be better in such a case to have supply of 32 V and use it for solenoid directly, and then only have one buck converter for the nano?

PerryBebbington:
I don't see any point to the double switching, just turn on and off the boost converter, unless you tried that and it caused a problem I cannot think of.

Good point. The circuit evolved, I first switched the solenoid, then wanted to switch boost converter too, that's the only reason.

I tried what you recommended but was not able to get it working. I was not able to switch the boost converter's 0V input with the nano. It was always on. I must be missing something obvious. Could you give me some hints on how the circuit would look like?

Thank for your help so far

What that downside when using Nano built in regulator? Will it eventually die?

If the ONLY thing is it powering is the Nano the built in regulator is probably OK. Does it get hot? By 'hot' I mean too hot to touch. My rule of thumb is that if it is not too hot to keep your finger on then it is not too hot. Linear regulators convert excess voltage to heat, so if you use a 12V battery and a linear regulator to provide 5V then 7/12 of the battery is making heat and not doing anything useful. I realise that's not true in this case because the battery is doing other things too, but keep in mind as a general principal. A buck converter swaps voltage for current, so the higher input voltage is reflected in the input current being less than the output current.

I tried what you recommended but was not able to get it working. I was not able to switch the boost converter's 0V input with the nano.

N channel MOSFET. Did you use one? Won't work with P channel. Show your schematic and I'll comment.

Thank for your help so far.

You're welcome :slight_smile:

Tip120.... The transistor is switching a very, very low current so the lower base current in it is likely enough.

Saving power, okey. I just wounder what the voltage from the booster look like at "powerup". Maybe okey. I assume You don't use PWM for it.

If You consider the Ding-Dong and the booster as one unit and switch the ground, (grounds) that unit it ought to work.

PerryBebbington:
If the ONLY thing is it powering is the Nano the built in regulator is probably OK. Does it get hot?

Yes, it is only powering the nano, I have no other things attached to the nano. So far I did not notice that it is getting hot, but I'll keep an eye on it

PerryBebbington:
N channel MOSFET. Did you use one? Won't work with P channel. Show your schematic and I'll comment.

Thanks. Yes, I did use a N channel. Shorty after the reply found the issue, forgot to remove one connection (that was remaining from the previous circuit, I didn't want to tear down everything :slight_smile: )

So I tried your suggestion, but it has the issue that the solenoid is not "explosive" enough to hit the gong with force. Could it be because the voltage of the boost converter is gradually increasing first from 12V to 32V. Or might it be an issue with current? Any idea to fix this?

You need to use a logic input N-channel MOSFET. A conventional MOSFET will not work.

Railroader:
You need to use a logic input N-channel MOSFET. A conventional MOSFET will not work.

Yes, I did use IRLZ24NPBF, thanks.

Railroader:
I just wounder what the voltage from the booster look like at "powerup". Maybe okey. I assume You don't use PWM for it.

If You consider the Ding-Dong and the booster as one unit and switch the ground, (grounds) that unit it ought to work.

No I don't use PWM. Unfortunately I don't know how the voltage looks like at power up, I don't have the equipment at the moment to measure it. I guess this has something to do with the issue I described in my previous post (when switching the grounds), not enough to ring the gong with force.

I'll not check Your MOSFET, believe in You.
Could You show us a drawing of that failing attempt? "Pack" the Ding_Dong and the booster together and switch their commom GND to the battory. NOTE that the Arduino GND must be connected to battory GND all the time.

So I tried your suggestion, but it has the issue that the solenoid is not "explosive" enough to hit the gong with force. Could it be because the voltage of the boost converter is gradually increasing first from 12V to 32V

Ok, so you tried and found that it doesn't do what you want. I consider that success because you learned something. My guess is what you said is correct, the voltage doesn't increase fast enough. Back to your original circuit.