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joe90
04-25-2006, 01:06 AM
I want to use the board of education basic stamp and PWMPAL to control a 2500W buck converter to charge batteries. One of my ideas is to put the stamp at the output of the converter and sense the voltage to see if it is at the charging voltage (~12 volts) then modulate a series of buck transistors as needed. I plan on using a voltage divider in parallel with the battery to protect the stamp. The battery has an internal resistance of 4milli-ohms. Will this work? Is there a standard way to protect the stamp from high currents?

bennettdan
05-05-2006, 01:33 PM
you can divide the voltage down and use a comparator curcuit if you plan to only charge at one voltage or a DAC chip for variable voltage.

joe90
05-06-2006, 12:56 AM
I will use the voltage divider. Thank you for the reassurance.

Since my posting I have decided to go with the SX-key. I will program it to input an analog signal and PWM. The extra speed of the SX-key minimizes the size of the buck inductor and the SX28 chips are $3.

Thanks,

bennettdan
05-06-2006, 05:34 AM
Yes I like the SX chips also, do you mind if I ask why are you needing to charge so many batteries?

joe90
05-07-2006, 02:28 AM
·This·is for a windmill application.

bennettdan
05-08-2006, 09:16 AM
I have played with windmills myself and they are interesting. I used a car alternator charging 4 batteries in parallel and one power inverter.

joe90
05-08-2006, 11:35 PM
Nice.

Did you isolate the charging of the batteries -- Did you use diodes or an eight output led transformer to separate the batteries? Or did you not isolate them and hook up the battery terminals directly to the output of the rectifier with wires.

bennettdan
05-09-2006, 12:21 AM
I used a one wire high output altenator off of older chevy cars, you can pick one up out of JC Wheitney catalog. No isolation just have a relay break the current from the alternator after fully charged and I run the alternator when a load is being pulled off the batteries. If you plan to run a load like a inverter all the time you can just leave the relay on and charge the batteries all the time. If you want to know when the batteries are charged I use a shunt and monitor the current into the battery .

bennettdan
05-09-2006, 12:41 AM
The most interesting part of a windmill is creating the collector ring so that the windmill so it car rotate and not bind the wires

joe90
05-09-2006, 02:32 AM
Thanks