Micro / Car / Power problem

[TKS]

Hi all,

i have a problem in a micro project.

the problem is that i hookup the micro to the battery of my car and while i start the car, the micro shutsdown / goes of..

when the power returns it doesn't switch on...

i need to do a reset / mclr pin to have it ready again....

are there any fuses who might help or what kind of circuit do i need to make / wich components to use soow the micro gets voltage while starting.

hope you all have ideas and share them

Regards,

TKS

 

[Nigel Goodwin]

Hi all,

i have a problem in a micro project.

the problem is that i hookup the micro to the battery of my car and while i start the car, the micro shutsdown / goes of..

when the power returns it doesn't switch on...

i need to do a reset / mclr pin to have it ready again....

are there any fuses who might help or what kind of circuit do i need to make / wich components to use soow the micro gets voltage while starting.

hope you all have ideas and share them

Regards,

TKS

I would suggest you feed the 12V power to the 5V regulator through a reverse blocking rectifier, and have a LARGE electrolytic on the input to the regulator. This will maintain power to the regulator when the battery goes low during starting - the rectifier prevents the electrolytic being discharged back through the starter motor.

You might also turn ON the brownout option in the processor, or even add an external brown-out circuit - examples are given in the PIC datasheets.

 

[TKS]

Many thanxs for your help!! sow far...

soow the best thing i can do is make a suplly for the micro right?
Can give me an example of an:

"reverse blocking rectifier, and have a LARGE electrolytic on the input to the regulator"

An electrolytic isn't the same as an elco right? wich value?? 470uF,2200uF
i thought i recently read that electorlitic has a max of 1uf

reverse blocking is it an diode??

Regards,

TKS

 

[Nigel Goodwin]

Many thanxs for your help!! sow far...

soow the best thing i can do is make a suplly for the micro right?
Can give me an example of an:

"reverse blocking rectifier, and have a LARGE electrolytic on the input to the regulator"

An electrolytic isn't the same as an elco right? wich value?? 470uF,2200uF

2200uF, 4700uF - something like that, in the thousands.

i thought i recently read that electorlitic has a max of 1uf

No, that's just about the smallest electrolytic you get.

reverse blocking is it an diode??

Yes, so it passes current from the car to the electrolytic, but not back the other way.

 

[TKS]

ok

If i get you,

You want to do this trick

You want to load the capp and the power it unloads can only be wasted/usted bij the 7805?

So in my case i also use some servo's, they are connected to 7806's
(2 in parallel with heatsink)

soow i noot to connect them behind the diode 2..

the sheme is like it is now...

Hope you can help a bit

TKS

 

[TKS]

Sheme

 

[Nigel Goodwin]

Re: ok

If i get you,

You want to do this trick

You want to load the capp and the power it unloads can only be wasted/usted bij the 7805?

So in my case i also use some servo's, they are connected to 7806's
(2 in parallel with heatsink)

soow i noot to connect them behind the diode 2..

the sheme is like it is now...

Hope you can help a bit

It depends if the servos will discharge the large capacitor, you might need to feed just the 7805 from the capacitor.