Circuit kit restarting problem

[roltex_rohit123]

I have designed a controller based circuit for my project. I have connected some accessories like heater and water pump across relays. but the problem is that whenever heater or water pump starts after relay click, the kit gets restarted. when the pumps or heaters are not connected then this problem does not occur. what could be a possible solution?

 

[alec_t]

The reset is probably being caused by interference being picked up at the reset input of the uC. Or the load current could be causing the supply voltage to the uC to drop. Make sure that the loads have adequate interference suppression components attached, that all wiring is as short as possible and screened, and that uC pins are all properly terminated (e.g. no floating inputs).

 

[roltex_rohit123]

The reset is probably being caused by interference being picked up at the reset input of the uC. Or the load current could be causing the supply voltage to the uC to drop. Make sure that the loads have adequate interference suppression components attached, that all wiring is as short as possible and screened, and that uC pins are all properly terminated (e.g. no floating inputs).

the circuit resets if the loads are connected. if the loads are removed the relays click but the kit doesnt restart. moreover if i connect electric bulbs instead of the heating coil and the pump motor, then the kits works fine too. what could be the reason and a solution for this problem?

 

[Reloadron]

The bulbs and heating element(s) are resistive loads and the pump motor is an inductive load. Something you can try is using an RC snubber network across motor and heater loads. A Google of RC Snubber will give you some reading. You should be easily be able to throw a quick snubber together and see if it helps. Also, make sure your uC is well isolated from the power driving the load.

Ron

 

[alec_t]

I agree with Reloadron. The heating element and motor are probably generating interference/voltage spikes and/or are lowering the uC supply voltage. (At least the relay back-emf at switch-off doesn't seem to be causing any problem.)

 

[roltex_rohit123]

The bulbs and heating element(s) are resistive loads and the pump motor is an inductive load. Something you can try is using an RC snubber network across motor and heater loads. A Google of RC Snubber will give you some reading. You should be easily be able to throw a quick snubber together and see if it helps. Also, make sure your uC is well isolated from the power driving the load.

Ron

Yes thats what exactly i was thinking of but i didnt knew what this was called. still your solution is very good. I'm definitely going to do this. reverse zener snubber.. thank you very much.

 

[roltex_rohit123]

thanks everybody. this was my first project microcontroller based developed in C. thanks to all those who have helped..

 

[roltex_rohit123]

sorry to interrupt again. the zener snubber doesnt seem to work. what could be a possible snubber appropriate for the situation. the uc is 8051 at 11.059mhz. relays are transistorized at 12 volts. load is around 2amp at 50hz 220v AC.

 

[Diver300]

You could try putting a capacitor between ground and the reset line. There could be interference being picked up by the reset line.

You also need plenty of suppression capacitors on your power supply lines.

 

[roltex_rohit123]

do you mean capacitor between ground & reset of uc? what i read of snubbers i need to connect resistance & capacitor across a diode. If it is so I dont know how to calculate the values for R and C

 

[Reloadron]

Can you provide a drawing of exactly how this is wired?

Ron

 

[4pyros]

do you mean capacitor between ground & reset of uc? what i read of snubbers

These are two different things.
The cap is for the Cu power lines and the snubber is for the relay coil.