Solar panel track back EMF problem by Car wiper motor

[spitso]

Hello all

Ive recently been working on a solar panel sun tracker circuit, found on this website **broken link removed**

The problem i need a hand fixing is i believe that my motor (in my case a car wiper motor) is producing back EMF, as it turns on/off my relay makes weird sounds aswell as little sparks can be seen on the inside contacts. If i continue running the circuit like this one 555 timer blows.
The circuit runs fine off a smaller hobby motor.

cheers for the help

 

[colin55]

Are you connecting the motor directly to the 555?
Have you included a buffer transistor?
Have you included capacitors and electrolytics across the motor wires?

 

[BrownOut]

In addition to bufferning, make sure you are using the diodes across the realy coils, and you can isolate your 555 from the rest of the power by using a 56 ohm resistor between the chip and the motor, relays, etc, and a 1uf capacitor connected between the junction of the resistor, chip power and ground.

 

[spitso]

Hey thanks for speedy response.
No 55 not powering motor directly.
at first i had 555 running relay and then relay running motor, recently i attached 555 output to power NPN transitor base and made that run a relay which ran the motor but still no luck.

yes i am using reverse bias diodes across relays.

i might try the resistor trick BrownOut mentioned. So i place the 56 ohm resistor from the output of the 555 to the relay?

 

[BrownOut]

So i place the 56 ohm resistor from the output of the 555 to the relay?

No! Place the resistor on the power pin of the 555 and connect the other end to the +12V, or whatever you're using for power. Then connect the capacitor from the power pin to the ground pin.

 

[crutschow]

To minimize sparking of the relay contacts (which erodes the contacts and generates EMI), put two diodes from each motor terminal (four diodes total) to the plus motor supply voltage (cathode to supply) and common/ground (cathode to motor). That will provide a path for the inductive motor current when the relays open.