Pro Micro - heat problems and desynchronization - help needed


I have a heating problem that causes desynchronization after 3 minutes of running of my 8 servo motors RDS3135. One on 4 servos also stop. The pro-micro gets really hot and regulator and heat sink also.

My setup is ;

1- Arduino Mega plugged to 9v power supply
with HC-12 transmitter on a breadboard

2- 2 breadboard connected to 12v powersupply and alimenting each 4 other breadboards (so total 8 breadboards)

3- On each 8 breadboard controlling each a servo RDS3135
I have 1 promicro, 1 HC-12, 1 regulator L7805CV, heat sink on each regulator, 1 capacitor 100nf, Electrolytic Capacitor - 1uF/50V.

Any idea what I am missing? Or should do to solve this problem ?

Your servo power supply is totally inadequate.

The servo stall current is 3.2 Amperes at 7.2 V, so your power supply should be able to supply at least 24 Amperes, at 6 to 7.4V, or have each servo powered by a separate 5 Ampere switching regulator, like this one, NOT a linear regulator like the 7805.

Do not use breadboards for power connections to motors or servos, as the tracks will burn out. Instead use flexible multistranded 22-24 AWG wires and high current connectors for each servo power connection, or solder the joints.

How many of what is connected to the Micro's 5V and output pins? Post wiring diagram.

Thank you jremington and JCA79B

I removed the servo from the chain and still the pro-micro was very hot.

This is the diagram

the pro-mini there replaced by pro-micro
and HC-05 by HC-12

regulator with heat sink

I really hope that is not your layout!

If you are using a 7805 - which you should not be as it has been explained that you should be using a proper switchmode "buck" converter module which has all its capacitors already on-board - then the three capacitors for the 7805 should be on the same three breadboard columns as the regulator itself otherwise you have a radio transmitter operating at an unknown frequency.

Or is this just a notional representation of something else you have wired up that is totally different?

Yes it is ... :confused:
I'm a newbee and got this diagram on
and replicated it.

I got suggestion for a stepdown DC-DC 5A this afternoon. Just got it.

I guess that is what you refer to ?

The Arduino 5V output can provide only a few mA, for example for a couple of sensors or LEDs. It MUST NOT be used to power motors or servos.

Use a separate power supply for everything else, and connect all the grounds. For 8 servos, your servo power supply must be able to provide on the order of 24 Amperes.

got this diagram on

It is wise to avoid that site, and Instructables.

OK, well, regulator spans the top end of three columns.
Just below it goes one 100nF ceramic between output and ground.
Next row down goes the other 100nF ceramic between input and ground.
Next row down are the connections to other parts of the circuit - output, input and ground.
Last row down goes the electrolytic between input and ground.

Actually even better would be the regulator itself in the middle of five rows, the ceramics in rows above and below, and the electrolytic on the row nearest the middle of the breadboard. This is how you arrange it when you design PCBs.

The Arduino 5V output can provide only a few mA, for example for a couple of sensors or LEDs. It MUST NOT be used to power motors or servos.

It is not at all obvious what parts he is using!

Best to start over with the entire circuitry.

Thanks to all your suggestions!

This a photo of one of the 8 boards

Yes, that looks like a radio transmitter.

I looked up that servo model number. I see it has performance specifications for 7.2V and 8.4V. Why would you run it on 5V? It won't run very well at all.

Then the 5V supply is totally inadequate. That regulator can only deliver 1A under ideal conditions. That ideal includes a large heatsink and no breadboard.

What are you really trying to do? Maybe we can help you select components which don't require an expensive 24A power supply.

IMG_20190519_131831 copy.jpg

Yes, that looks like a radio transmitter.

It does, doesn't it? :grinning:


I'm trying to control the rotation of 8 servo motors (RDS3115 - I made a mistake in my description not RDS3135) individually rotating at different angles from data sent by a computer without any CAT6 (which I had in the begining). Ideally the computer can be set in a room located in the different place than the servos (100 meters of distance).

RDS3115 specs
Operating voltage: 5V ~ 7.2V

This is the transmitter-receiver HC-12 that we are using.

I'm an artist and this is my first time I work with electronic. So I am testing things at the moment.

Ok. That makes a difference. 1.3A stall current at 5V.

Since you probably won't stall them all at the same time, a power supply in the 5-8A range would probably work.

Do you have the wireless part working without the servos.


The two capacitors you have connected to the LM7805, CONNECT them directly to the 7805, not via half a dozen bits of wire and connections.

Connect the SERVO 5V and gnd wires DIRECTLY to the LM7805, not via half a dozen bits of wire and connections.

Measure the 9V power supply while you are moving the servo.

Thanks.. Tom.. :slight_smile:

If your setup function attaches all servos at the same and they all try to go to default position at the same time, that could be a huge load on power supply. I usually put a 200 to 300 mS delay between attaches.
If your servo's speed is, for instance, 0.15 seconds / 60 degrees (150 mS), it might take 450 mS for a 0 to 180 swing.

servo3.attach(servo3Pin); // etc.

If you don't want to post your code, at least post your setup().

Thank you all for your suggestions which I will test in the next few days.

About the wireless part, the emitter is on a separate section with an Arduino Mega (probably an UNO later).
The receivers are on on the same circuit of each pro-micro for each servos.