[SOLVED] automotive relay problem to microcontroller

[ltsharma]

i've installed microcontroller motorbike display system project to my motorbike, my motorbike having automotive relay to horn switch, when the horn button is pressed and released the microcontroller is restarts, even ive added freewheeling diode to relay, it is the main problem of it, what to do??????????????????

horn schematic

 

[snishanth512]

when the horn button is pressed and released the microcontroller is restarts, even ive added freewheeling diode to relay, it is the main problem of it, what to do??????????????????

View attachment 92805

Did you measure output current at the relay output?????

What diode did you use????

Measure : Voltage at the output of the battery. And maximum current that can be drawn from it.

 

[ltsharma]

im using in4007 diode, keeping pressed horn switch not effecting, while releasing switch it MCU will restarts

 

[chuckey]

Horns are just as inductive as relay coils, so fit a free wheel diode across it (or the relay contacts). You do not show the return from the horn to the battery. Often the horn earthed a to the frame and you just send a live to it to actuate it. Could be that the current through the frame is getting into your micro.
Frank

 

[ltsharma]

ohhhhhhh.... this one i dont know,,,, the metalic horn is also inductive load !!!!!!!!!!!!, i given FW diode for relay only :O
the horn is

????????


also same problem with starter motor....

and IN4007 is ok as FW diode?????

 

[ltsharma]

with IN4007, its not worked, same problem remains, connected for both horn and relay. (Battery: 12V 9Ah ) battery is enough i think

 

[pranam77]

You may check voltages before and after the 5 volts regulator powering the microcontroller, when the horn is activated. Confirm that the voltage is in limits of the Micro and doesn't drop. Suppresor diodes from TVS works well in place of 1N4007.
Cheers

 

[chuckey]

Inside the horn is a vibrating set of contacts that spark. it could be that the sparks are radiating directly which is being picked up by some lead running to your micro. Make sure that the metalwork of the horn is connected by a short wire to the frame, this will act as a Faraday cage and stop the case acting as an aerial. Now connect some low value DISC capacitors between the connectors and the frame, 1NF should do. This should now cause the spark power to loop around the case/ frame. Clutching at straws, to stop any interfering voltage going down the power line, put a radio frequency choke in it as close to the horn as possible. Be careful of the operating current, it could be 5 A or more.
Once the above has been done there is no more to be done at the horn end. The next area would be at the micro end to make sure that its supply voltage does not have any noise on it and any input lead to the micro is not acting as an aerial.
Frank

 

[ltsharma]

when horn is pressed, there is no problem, when i release the horn it will restarts

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You may check voltages before and after the 5 volts regulator powering the microcontroller, when the horn is activated. Confirm that the voltage is in limits of the Micro and doesn't drop.

when horn is pressed, there is no problem, when i release the horn it will restarts

 

[Venkadesh_M]

Try a Big 2200UF capacitor near to Micro controller, all the best....

 

[ltsharma]

now its having 1000uf already............... is 2200uf will do for sure?

 

[davoud]

It is better to show your schematic. If you use 1000uf for regulation and still have problem so i think you have a problem in your circuit board. please check connection between your circuit and bike electric system's such as : inputs , outputs and electromagnetic noise ...
Also I think you should use fast diode instead of your usual freewheel diode

 

[Venkadesh_M]

try it.. If still problem persists connect a diode in forward direction to relay. Else put additionallsupply for better reliablity...

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disconnect the horn and check the relay operation.. If its not the problem with relay then its horn only and you will need of aditional supply for sure..

 

[tpetar]

Test and check all wires, relay, horn individually, measure battery voltage when relay turn horn on.

Try to use uC on 3,3V if possible.

Add 100nF on uC close as possible to Vss/Vdd pins.



Post actual circuit.



Best regards,
Peter

 

[ltsharma]

Actual power supplay ckt

 

[tpetar]

Remove Graetz bridge, D1 and D2! Why you use this ? :shock:

In thread first post in your circuit you mention diode near relay, that diode keep.

Before 7805 voltage regulator put 100uF - 220uF, after regulator 10uF and 100nF on end.

Add an additional 100nF close to Vss-Vdd pins on uC.



Best regards,
Peter

 

[Venkadesh_M]

you have to add a lot of cap in left hand side of the circuit...........................

 

[davoud]

You Put 1uf at right side of regulator. put 1000uf before regulator and 330uf after that.
2-reset circuit of your micro-controller : I think you should survey that (you should use related circuit for RST pin at the datasheet).

 

[ltsharma]

Remove Graetz bridge, D1 and D2! Why you use this ?

In thread first post in your circuit you mention diode near relay, that diode keep.

Before 7805 voltage regulator put 100uF - 220uF, after regulator 10uF and 100nF on end.

Add an additional 100nF close to Vss-Vdd pins on uC.

1)i think bridge gives some more protection for transient voltage of relay
2) OK
3) is i need to use both 10uf & 100nf??
4) 7805 is very near to uC.

You Put 1uf at right side of regulator. put 1000uf before regulator and 330uf after that.
2-reset circuit of your micro-controller : I think you should survey that (you should use related circuit for RST pin at the datasheet).

sry that is not 1uf that is 1000,, but right side

i've used this reset config

 

[tpetar]

1)i think bridge gives some more protection for transient voltage of relay
2) OK
3) is i need to use both 10uf & 100nf??
4) 7805 is very near to uC.

First make this to work, later you can play and experiment with protection and other additional things.

This is not hard to do, and do not require too much effort.

10uF and 100nF are quite different values, each have their purpose.



Best regards,
Peter

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What voltage you have when load is activated you didnt say that ?

What is capacity of battery ?

Battery is healthy ?