PWM control problem with 7809 and arduino

Hello, I use the following circuit to control rpm of 2-4 dc motor an I face this problem. I use a generator for P.S.(12-25V DC) of motors I use a 7809 to give 9V to arduino(as in the figure). All until now is ok. When any of the motors needs some more current, a bigger current pass through the 7809 and burn it. If I use another P.S. for arduino for example 9V battery the circuit working properly.
I can’t understand why thiw happens with 7809. Is there anyone who can help me please?!?!?!

Sorry but that image is basically unreadable, not enough definition.
Please view your posted image.
One thing I do notice is you have no capacitors round the 7809, if you look at the spec sheet you will see they show two capacitors on the input and output of the IC.
Place these caps as close to the 7809 as possible, it hels with load regulation and stability.

What MOSFETs are you using and why have you got MOSFETs with open SOURCE terminals.
In your next schematic, can you use the correct symbols for the MOSFETs.
Are the MOSFETs logic level gate type?

I use a generator for P.S.

Sorry what are you using to power your project?

Tom… :slight_smile:

I use a 1000uF capacitor at input of 7809. The Source is not connected by mistake. The mosfets are IRFB4610 and I use a power generator to supply arduino and motors and when I use a different PS(for example 9V battery) for arduino I haven’t any problem.
I hope this photo is better.

dc motor PWM.pdf (45 KB)

That looks pretty good. I would personally use a 7805 or the modern switchmode equivalent to power the Arduino through its 5V pin. Your power to the LCD backlight is coming from the Arduino's 5V regulator, which might be over-stressing it.

What heatsink do you have on the 7809? Have you calculated the power dissipated by the regulator? Have you calculated the temperature rise for your heatsink?

You circuit as drawn doesn't pass any motor current through the regulator, so I don't
think your diagram corresponds to the actual circuit.

Leaving the source disconnected of the MOSFETs is probably a Bad Thing.... What voltages
are we talking?

Certainly if the source isn't connected then the gate-source breakdown voltage will
apply to the gate-drain voltage instead (not normally something you have to
worry about).

Decoupling caps have already been mentioned - always needed, never optional.

Circuit is as I draw it on the second post. Sourcew ware not connected only on the first schematic not in actual circuit.
We talking about 12-24V DC and about 10-15A.
I placed a simple heatsink on 7809 because I saw that when I use a Lab Power Supply it works good until 30V(input) without any big raise of temperature.
I think that monfet and motor doesn't affect on arduino that is the reasion I am really confused.


Thanks for the pic, the smaller sized pdf is much better thankyou.

a power generator to supply arduino and motors

Can you post a picture of your power generator, what are its specifications?
Also a picture of your project? So we can see if there are any problems with your layout.
It sounds like we have a problem with language translation.

The 1000uF capacitor will not help the 7809 performance because of the diode D5,
Leave the 1000uF where it is but PLEASE add the capacitors that are shown in the data sheet for the 7809 in the circuit.

when I use a different PS(for example 9V battery) for arduino I haven't any problem.

Tends to tell you that the 7809 is having problems.
It could be due to your "generator".
Can you measure your "generator" voltage before and during the motor highspeed that causes the problem.

Give each of the MOSFETS its own gate resistor, try 470R instead of 33R resistors.

Tom...... :slight_smile:

Oh yes, I missed that, if you parallel MOSFETs give each a gate resistor… There’s a differential
oscillation mode you need to damp.

Hi, Goodmorning, MarkT.

I hate coloured schematics, good old BLACK and WHITE would have made that schematic so much easier to read.

Tom...... :slight_smile:

I use power genarator like this

with output 12V DC 15A

The output have a lot of ripple(arduino didn't turns on) but after I add a bigger capasitor(1000uF) the DC was ok.
Why D5 is a problem?
As I saw yesterday night, when I turn on any of the motors the DC ripples again and when any of the motors needs more current, the ripple is raising. Is there a possibility problem caused by the motors??

Today I will change gates' resistor and I will add a 100uF capacitor on the output of 7809.

Hi, :o :o :o :o :o :o :cry: :cry: :cry:
A generator will be producing all sorts of ripple and spikes, I'm surprised it has survived this far.

I would actually suggest you use a 12V battery to as your supply with the generator, if you have to have a generator, charging the battery.

Not direct generator to arduino with little filtering, also I would be worried about voltage spikes from any generator system connected directly to electronics.

If you are going to use something like that, you will need more than 1000uF of smoothing, the more you increase the current required by the motors, the more ripple you have, 1000uF is nowhere near enough.
10,000uF at least.

If you replace the 1000uF with 10,000uF , place the 1000uF between the input of the 7809 and gnd.

The 7809 needs capacitors connected to it as in the data sheet to help with response and stability.
D5 is protecting the 7809, but the 1000uF is not helping the 7809 with response and stability.
The 1000uF is only trying to filter the DC ripple.
Please read the 7809 datasheet.

Tom..... :slight_smile:

Thank you all about your answers and your advices there were absolutely helpfull. Finally power generator ripples and spikes was the problem. I try to work with another one and all was fine.