[SOLVED] automotive relay problem to microcontroller

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1) battery voltage drops max of 0.7-1V when horn activated, when horn released suddunly it goes zero and comes back 10 12.5 to 13V
2) battery is 12V 9Ah (maintenance free)
3) battery is very healthy because its 1 month old
 

ltsharma said:
1) battery voltage drops max of 0.7-1V when horn activated, when horn released suddunly it goes zero and comes back 10 12.5 to 13V
2) battery is 12V 9Ah (maintenance free)
3) battery is very healthy because its 1 month old
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How you measure voltage with digital instrument ?

Battery can be 1day old and can be bad. This is not criteria to identify battery health.
 

tpetar said:
How you measure voltage with digital instrument ?

Battery can be 1day old and can be bad. This is not criteria to identify battery health.
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some times goes zero, some time some 9V like that, digital meter is slower,,,, i checked across battery.

i think battery is good, Bcoz, starter is running perfectly, horn has perfect tone, if headlight is switched it drops max of 0.5V. and my project always shows its voltage level as 12.6 to 14V

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did u tried without horn
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no,,, have to...........
 

Voltage in electrical system must be constant without such big oscillation down to zero, 9V, 10V 12V .... . Voltage must be constant minimum 13,8V and up to 14-14,4V when engine working, when engine is turned off voltage should be battery voltage range. Additional to this when you apply some load to system voltage should go down, lets say minimum to around 10V when you starting or have lights on or other heavier loads, but never zero in any case on any short or long period.

You should not have ever voltage interruption in electrical system in car or motorbike in any case. Only when you remove battery from system and engine is turned off.

Check electrical system, check all connections and wires.

Check all relays connections and contacts.



Problem is not located at voltage regulator or microcontroller circuit section.


7,5V-8V is minimal needed input voltage for 7805 voltage regulator to achieve 5V on output.



Best regards,
Peter

;-)
 

1) did you use large capacitance before regulator ?
2) did you use suppressor or fast diode instead of 1n4007 ?
3) did you use ferrite bead according to datasheet that attached for you ?
4) what kind of your micr ? pic avr nec ?
5) If your micr is avr or pic I think you should replace your reset circuit :
your circuit
correct circuit :


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http://www.picbasic.co.uk/forum/showthread.php?t=7814
 

1)yes, 1000uf & 104
2) No, i have to buy that... what is that really?.. any part numbers.
3)what kind of ferrite bead i need to use, value???
4) microcontroller is 8051 (NXP 89V51RD2)

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1)yes, 1000uf & 104
2) No, i have to buy that... what is that really?.. any part numbers.
3)what kind of ferrite bead i need to use, value???
4) microcontroller is 8051 (NXP 89V51RD2)
 

Ultra fast like MUR8100
for ferrite bead you can use a usual ferrite bead. you can find it connected to power cord or data cord.Also you can make it by a toroidal ferrite.
please goggle it.
 

tried >

1000uf right, 100&0.1 uf left of regulator, no changes
100uf across VDD of uC,, goen caes!! uC not booted, always in rest state, replaced 0.1 worked but no change in relay reset,
have to buy TVS diode....
 

You searching problem on wrong side, first check why your electrical system have power interruption, and check voltage drop below minimum voltage needed for 7805 voltage regulator to work.




Best regards,
Peter
 

isolate the uC by using a diode..........

+v ---------diode-------------capacitor [to ground] ---------------uC

that should keep the horn from affecting the power supply to the uC

also decouple [ using 0.1uF capacitors] the uC - as close as possible to the uC, a choke might also help

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as tpetar indicated there are 3 problems with an electro-mechanical load, such as a horn;

1 noise
2 near short-circuit which is very brief when the load starts and causes voltage to drop to near zero for a few milli-seconds. this is unlikely to show on a DVM
3 back emf

It sounds, at first, you addressed the back emf issue. The near-short condition, viewable on a scope, is addressed by isolating the power supply via a diode [in series] - before the regulator.
Others have mentioned some solutions to noise - I would use a ferrite choke rather than beads, however. And use 0.1uf caps on either side [its called a pi filter].
 

tpetar said:
You searching problem on wrong side, first check why your electrical system have power interruption, and check voltage drop below minimum voltage needed for 7805 voltage regulator to work.





Best regards,
Peter
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sorry for my stupidity,,, its a multi-meter problem, meter's probe and battery gone,, that's Y its showing wrong voltage values, like fluctuating,,, now changed both working perfectly.....
 

ltsharma said:
sorry for my stupidity,,, its a multi-meter problem, meter's probe and battery gone,, that's Y its showing wrong voltage values, like fluctuating,,, now changed both working perfectly.....
Click to expand...

Its Ok, just try to make good measurement and see what's happening with voltage. For me this is first step for any next step.



Best regards,
Peter
 

I've faced with a similar problem few years ago.This problem occurs when you feed both side of digital and analog load, connecting to one power line so the noise will cause to hanging the uC.try to use two different regulator for the uC and the horn.
 

This is happening because, the Horn is using a higher power to operate. so it will drain higher current for a short period from the battery.Take the the following steps to solve this.
1. Turn off the BROWN OUT circuit in ur micro-controller
2.use a SMPS based power supply insted of Linear one.
3.Use Fast Switching Shottky diode for freewheeling

For more suggestion,you have to post the detailed design
 


1. im using 8051, i think 8051 don't have that one
2. means buck converter ( https://forum.allaboutcircuits.com/showthread.php?t=78805 ) is this one?
3. i bought mur8100 for freewheeling.
 

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