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Topic: Car battery voltage regulation for ATtiny85 (and other MCs) (Read 1 time) previous topic - next topic


An LM3914 would be a much better deal as a voltage monitor and can easily be expanded to a spread type of meter that reads a small range of voltages...
There are some relevant app notes in the data sheet and I'm Sure that Mr Google has a big lot of answers if the data sheet doesn't,
Data sheet attached...

--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard


So I went ahead and built my regulator, there it is below. It worked alright when I just had it on a breadboard but I haven't got to try the board on my bike since it's a little too late to be revving my bike up.

Also, for everyone saying that I need a 0.1 uF across Vcc and GND, well there already is one. The 0.1 uF capacitor's pos and neg nodes are on the same nodes as if I were to put one there distinctly.

You need at least a 100uf cap on input side of the LM7805 in this application as well as a 0.1uF on the output.  Also, as already suggested put a 0.1uF across Vcc and Gnd of the ATtiny.  If you can get a hold of a 50mH to 100mH choke rated at twice the current your circuit draws would also be very nice and quite possibly a requirement.  I am assuming your circuit draws less than about 100-200ma.  Those 4-amp automotive radio filters are pretty bulky.

BTW, what kind of bike is it?

It's a 1996 Ninja ZX6.


Okay, let us know how it works out.  The ZX6 electrical system, while not really clean, would be cleaner than something like a KTM EXC.  If it still gets upset, the choke would be the next thing to try.  Something like this:
Facts just don't care if you ignore them.


I would still include ZD1 and D1 per the schematic in your second post. ZD1 protects you from high voltage spikes and D1 protects from reverse voltage spikes. The parts cost just pennies.


I have blown up 78L05 regs before by not using input capacitors, Capacitors are a must end of. The theory goes one 10+uF and a 100nF each side but i see that these days many dispense with the 100nF - no comment there I'm not such an expert.

You can use an lm7809 for your 9V - whats the problem ?

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