Voltage Dividers / ADC input / Protection

[kcarring]

I have been trying to figure out how to use my PICAXE ADC input to tap a voltage divider to then detect a battery charge level.

I got started into it... and then... it all came back to me...

With Bedini style circuit, the spike, and what that might do to the chip.
And so I halted.

I am thinking that the ADC would have it's own power linear regulated to 5V. Just for simplicities sake and stable reference.

If anyone could point me out in the right direction, that'd be great. The main goal is a battery swapper, basically... but I thought I'd start this thread, because there could be a multitude of reasons (different ones) you might want to do this.

Thanks.

[citfta]

I don't have time right now for a long answer but I think the easy way to protect the input to the ADC on the Picaxe is to put a .1 uf cap from the input pin to ground. After your voltage divider the spike should be so small the cap should easily catch it and protect the input. Also the battery should catch most of the spike unless it is badly sulfated. I am assuming you already know how to calculate the values for the resistors for the voltage divider circuit. If not I can help with that when I have more time. Gotta go.

Carroll

[kcarring]

I don't have time right now for a long answer but I think the easy way to protect the input to the ADC on the Picaxe is to put a .1 uf cap from the input pin to ground. After your voltage divider the spike should be so small the cap should easily catch it and protect the input. Also the battery should catch most of the spike unless it is badly sulfated. I am assuming you already know how to calculate the values for the resistors for the voltage divider circuit. If not I can help with that when I have more time. Gotta go.

Carroll

Thanks Carroll that should get me rolling

[citfta]

Here's an interesting page I was just sent to from another site. There are some examples here for using the Pic to monitor battery voltage. I thought you might find them helpful.

Later,

Carroll

Poormans Multitasking - Picaxe