#mosfet disconnects Mega board

1 messages · Page 1 of 1 (latest)

cursive sphinx
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Hi all,

For backlighting my overhead panel I'm using a single large backplate with 7 LED strips hotglued on the bottom. Each STRIP IS approximately 70cm in length . This worked fine with a 12V 2A power supply and a simple 12V LED dimmer.

Now I'm trying to replace the dimmer with 3 Mosfet boards to control 2x2 and 1x3 LED strips. Even connecting the 12V 2A power supply to a single Mosfet that controls only 2 LED strips, the Mega disconnects within seconds to a minute. For the short duration that it stays connected, it does work fine.

The LED strips are 12V 240 LEDs/m. To power 5m in total, I came to understand that a 12A power supply would be recommended. The Mosfet is rated up to 5A but it is stated to install a heatsink above 1A. Tbh I'm not sure how I should realise that in the setup.

I've tried using a 12V 4A power supply on single Mosfet with 2 LED strips but it changes nothing. I also made a direct ground connection between the power unit and the Mega. Again, no change. When I switch off the PWM in the Mobiflight output config the board does NOT disconnect. But that would leave me with only ON or OFF.

The only reason for changing the normal 12V LED dimmer to Mosfets is that my dimmer knob now also controls the backlight of my Battery voltage LCDs (KAV).

In hindsight it would have been less stressful to make a gearing system to make the dimmer knob control both the potmeter of the LED dimmer as well as the potmeter that controls the LCD backlighting.

But if anybody could advice me on how to prevent the mosfet from causing Mega disconnects I would be very grateful.

urban hamlet
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What mosfet board you use? What are its ratings?
How is it connected? Show us connection of entire setup

cursive sphinx
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Hi Marek,

Here is the Amazon link of the Mosfet board.:

https://amzn.eu/d/0zwpHvW

I will upload a few pictures showing the connections shortly.

5PCS Driver Module 3.3V/5V IRF520 MOSFET Driver Modules PWM LED Tra...

Specificaties:
Grootte: 3,5 * 3,2 cm / 1,3 * 1,2 inch
Spanning: 3.3V, 5V
Poort: Digitaal hoeveelheidsniveau
Uitgangsbelastingsspanning: 0-24V
Uitgangsbelastingsstroom: <5A (koellichaam nodig als> 1A)
Platform: SCM, voor ARM, voor
Gewicht: 4g (ongeveer)

Pakket Omvat:
5 x stuurp...

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I do have to add that my overhead uses 7 Megas connected to the PC via a powered USB hub.

cursive sphinx
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The actual Mega in the overhead contains dozens of LEDs and switches besides the Mosfets.

vapid phoenix
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it looks like you connected the mosfet vcc to the mega vin pin. The mega vin pin is for power input, not output.

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You should try connecting it to the 5v pin instead

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Also connect the 12v power supply GND with the Arduino GND.

cursive sphinx
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Hi Jaime-Leon,

Thanks for your reply,

The mosfet VCC is actually connected to the 5V pin on the Mega. And I do have a ground wire connected between the 12V power supply and a ground pin on the Mega...that is the single black wire in the picture. On the actual Mega in my overhead it is properly fixed to the Mega.

vapid phoenix
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ok, it was hard to see in the picture

cursive sphinx
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I have the same setup in my pedestal. To test that mosfet so far has only been connected to about 50cm of LED strip in total. That one does not cause any problems.

vapid phoenix
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I would look for any wiring issues. If the mega disconnects after some time, I would suspect it is because it is overloaded, leading to a board reset.

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It also seems each 70cm strip can draw 1.6amp assuming 20mA per each three-led cluster. I don't know what the strip current rating is.

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So a heat sink for the mosfet is required.

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when you say the mega board disconnects, do you hear the windows usb disconnect sound?

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I am trying to determine if the disconnect is actually the mosfet overheating.

cursive sphinx
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Yes I hear the windows disconnect sound. Mobiflight stop running and often when I then check which modules are still connected, the relevant Mega is no longer showing.

vapid phoenix
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Does the mega board feel hot when the disconnect occurs?

finite estuary
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does it disconnect also I'd you don't run mobiflight or turn on the led strips?

cursive sphinx
cursive sphinx
vapid phoenix
finite estuary
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all of the examples in google dont connect the VCC at all

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and well, the signal pin is really the only thing the mosfet needs

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when you consider our own MOSFET wiring

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its just GND and the signal pin

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My assumption is that the board can work both ways - either via the Arduino's 5V pin (it comes from the USB port, so it has ~500+mA current available)

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in which case you connect the VCC

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and alternatively the screw terminals with external higher voltage like 12V

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I am wondering if VCC and VIN are somehow even connected?

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so the blue image is from:

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"Notice that the VCC pin on the module is not connected to anything. Also, the Vin and V+ pins are just tied together."

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"In retrospect, you don’t need the connections from the power supply positive to the module V+, they don’t actually go anywhere. Only the connection to the LED strip positive common is required."

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you could beep it through with a multimeter, the worst case is it has been feeding 12V to your Arduino 5V pin, which would perhaps understandably upset the USB controller

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but it would need to be checked what is connected where in that circuit board to know any better

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but try without the three-pin rail VCC connected

cursive sphinx
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Thanks, I will try it without the VCC pin connected, first thing tomorrow morning and report back.

cursive sphinx
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Update on the mosfet issues:
I've working on it all day again. And finally some progress made but I'm still not 100% sure what the real issue was. And I'm not fully out of the woods yet. There is still a Mobiflight restart required after about 10 minutes. But at least 10 minutes of good operation is much better than the average of 10 seconds yesterday.

What was done today:

  1. I provided each Mosfet with its own dedicated power supply. 2x1.5A for the 2 sets of 2 strips, 1x2.0 ampsA for the set of the 3 strips.
  2. One of the signal wires has been refitted with another dupont connector as the previous one was apparently having an intermittent bad connection.
  3. I've tried NOT connecting the Mosfet VCC pins to the Mega 5V pins. But it does not seem to make a difference. At the moment they ARE connected to the Mega 5V pins.
  4. I've connected the Mosfet that controls the set of 3 strips to another Mega.
  5. I've disconnected the Mega that controls the other 2 mosfets, from the USB hub and connected it directly to the PC. This is very undesirable because I have dozens of USB devices connected to the PC to run the whole cockpit.
  6. I've received an update for windows 11 which I installed and restarted the PC. Several PC and MF restarts during the day because of boards disconnecting everytime.
cursive sphinx
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Still very much WIP but a nice upgrade. However the phone camera doesn't properly show the actual dimming of the backlighting and the LCDs. IRL it looks better 😀.

timber moss
timber moss
finite estuary
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I am trying to think why it would cause the arduino to reset the usb connection though

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its strange

cursive sphinx
cursive sphinx
timber moss
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When you say the board disconnects... does it reconnect when MF is restarted? Or does it require being physically unplugged and then plugged back in? Or a PC reboot?

cursive sphinx
# timber moss When you say the board disconnects... does it reconnect when MF is restarted? Or...

Unfortunately it has been all over the place. Sometimes the Windows disconnect sounds, sometimes it doesn't. Sometimes Mobiflight stops working but I can still press the MF stop button, more often it changes into the run button. Sometimes MF would freeze and I had to close it with task manager. Sometimes the boards would show still connected while they are not, sometimes they reconnect upon MF restart, sometimes I have to reboot the PC...all in all not very helpfull for troubleshooting. I have lowered the max output of the mosfets to the strips by using the MF pwm interpolation function to a max of 100 iso 255. That does seem to stabilise the situation. I will be doing more testing after I have fitted the resistors and removed the 5V to the VCC.

finite estuary
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is it just this one arduino or do you have problems with all of them?