I am trying to make a power wheel car remote controlled.
My setup is: I am using a 4 channel relay module to control the car's motor in forward reverse motion and the relay is getting the signal from a RC receiver. I have a 12V lead battery. The relay board and the receiver board needs 5v power so i used a 7805 IC for 12v-5v conversion but the 555dc motors are directly connected to the battery. So basically all the components are connected to same source.
Problem:
Every thing works fine if I don't connect the motors. all the relays turn on and off with the remote accordingly. And the output wires for the motors are also changing the polarity accordingly
But when i connect the motors and turn the relay on using the remote it turns on and off very fast, maybe 15-20 times a second or more.
At first i thought maybe the motors are drawing too much current or causing a voltage drop which is causing the relay module to shutdown. so just to check I used only one 5v dc toy car motor but still the same thing happens.
Also I used a laptop 19v charger instead of the battery for more voltage or current and it's same.
I haven't tried using capacitors for the regulator output as i don't have enough idea which one to use.
However when i use a separate 5v battery source for the relay and receiver then it works properly with both the laptop charger and 12v battery. so something is wrong with my main power source when i use only one source. How can i use the 12v battery for everything.
I have attached the diagram also.. plz i need help. Thanks for reading.

 

Hi T45,
Welcome to AAC.
The 7805 must-have capacitors on the input and output side.
E

 

Hi T45,
Welcome to AAC.
The 7805 must-have capacitors on the input and output side.
E
View attachment 325802

The 7805 must-have capacitors on the input and output side.

Could you please explain a little bit why adding the capacitors is such a big deal.. i mean i know there is voltage or current drop for the motors but the regulator is still giving 5v output right and the relay and the receiver combined dont need much current maybe 180mA. so is this a lot for the regulator to provide when the motors are connected. I am actually new in all these..so excuse any mistakes.

 

A three-terminal linear voltage regulator such as 7805 is an analog feed-back control system.

It takes a sample of the output voltage and applies a gain correction to the driving amplifier. In every feed-back control mechanism there is a time delay between output sense and feed-back control. If this is not done properly, the control mechanism has a tendency to oscillate.

The purpose of the input and output capacitors is to prevent oscillation.

 

The Big Deal with the capacitors and the voltage regulator really is a big deal. The regulator is very fast, and without the capacitors it can easily oscillate at maybe 20 megahertz, or some other high frequency. I discovered that many years ago. So you do need to trust us that at least the 0.1 mfd capacitors are not optional.
But as for the relays, that chatter is indeed a symptom of too much resistance someplace in the relay operating circuit. And the experiment with the small motor shows it is not in the "big motor" power loop, but somewhere in the relay control wiring. I see control signal wires from the RC receiver but no control signal return wire. That could be the source of the problem. Powering a relay reducing the control signal.