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#### Wizzard

• Jr. Member
• Posts: 23
##### Math and conectivity Check please.
« on: February 17, 2009, 02:03:15 PM »
I am going to try to implement the circuit that Admin has in the Battery Monitor Circuit diagram on my Axon and I want to make sure my math is correct and my hook up procedure is also correct. (I would hate to fry something in my Axon).

First I will be using a Axon and it looks for a upper limit of 5v on a analog input so Vlog-1 would be 4. then I am using a 7.2 volt supply and if it is fully charged it is actualy about 8.6 volts so 8.6 divided by 4 equals 2.15 and 50,000 divided by 2.15 means I need a 23,200 ohm resistor in the R2 location. If this is all right I plan on doing the following.

I connect P1 to my positive lead between the battery and my Axon Positive Bat input pin (P2). then I connect P3 to a analog input ADC1(inside  pin) on my axon and P4 to the ground (outside pin) on the axon?

My image of my schematic is not inserting properly (my bad) please look at the PDF attached.
Thanks Wizzard
« Last Edit: February 17, 2009, 02:14:51 PM by Wizzard »

#### pomprocker

• Supreme Robot
• Posts: 1,430
• Sorry miss, I was giving myself an oil-job.
##### Re: Math and conectivity Check please.
« Reply #1 on: February 17, 2009, 04:16:14 PM »
I have an article in my blog concerning this, it walks you right through it:

http://pomprocker.blogspot.com/2009/01/battery-monitor-voltage-divider-circuit.html

Feel free to leave comments on my blog for others to see regarding any questions or discrepancies

EDIT: the only thing in my Blog I don't mention is the current factor. Once you get the resistor ratio you need, you will then need to pick the pair that gives you the current you need.
« Last Edit: February 17, 2009, 04:17:46 PM by pomprocker »

#### Wizzard

• Jr. Member
• Posts: 23
##### Re: Math and conectivity Check please.
« Reply #2 on: February 17, 2009, 06:32:02 PM »

I have an article in my blog concerning this, it walks you right through it:

http://pomprocker.blogspot.com/2009/01/battery-monitor-voltage-divider-circuit.html

Feel free to leave comments on my blog for others to see regarding any questions or discrepancies

EDIT: the only thing in my Blog I don't mention is the current factor. Once you get the resistor ratio you need, you will then need to pick the pair that gives you the current you need.
Good blog and thanks for the pointer to it. Now I have to read some of the others. I guess I still need a little confirmation on a few things. since I want to measure the voltage on the unregulated buss on my axon. Can I just tie the positive side of this circuit to the center pin on one of the unregulated sets of three pins? like E2? and them take the ground side to the outer pin of ADC0 and the point where the 2 resisters come together to the inner pin of E2?

yes?

no ?

also any tricks to the code for getting the reading?
« Last Edit: February 17, 2009, 06:33:27 PM by Wizzard »

• Supreme Robot
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