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Forum Index : Electronics : PicAxe Charge Controller
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wphfla Newbie  Joined: 31/12/2006 Location: United StatesPosts: 3 |
Hello and Happy New Year to all in the Southern Hemisphere! I'm a new member here, but have been a frequent visitor for several years. Gizmo's enthusiasm for the PicAxe chip got me interested in this little gem. I've put together a schematic of a 12V charge controller as a first project. It would be much appreciated if someone here with some electronics knowledge could review and critique my design. Controller My electronics ability is quite limited. The battery bank (12V - 345 Ah) is charged from a rectified 80-100 Watt, 3-phase wind generator. My inverter is msw 1250 watt with a shut down voltage of 11.5VDC. Thank you in advance for your assistance. Kevin |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Kevin. That circuit looks fine. I would have left out the 3 resistors and diode before the 7805 regulator, but they do provide some protection to the regulator and wont hurt to leave them there. I also would have used a MOSFET instead of the transistor, but I like MOSFETs and have heaps in my parts drawer. Have you written the code for the PicAxe? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| wphfla Newbie Joined: 31/12/2006 Location: United StatesPosts: 3 |
Thank you for your input Glenn. I've not yet written the code, but I do have the psuedo-code laid out in my head. Just need to get it down - should be straight forward and quite simple. The transistor was chosen because I have a bunch on my bench. I've tried to build shunt controllers with transistors, but I have a devil of a time getting the base biased correctly. Hopefully this circuit will help avoid that problem, and I do like the thought of being able to adjust the circuit with code rather than reworking an entire circuit. The circuit is very simple, but one must crawl before one walks. I really do enjoy this site and the philosophy of your members. Regards, Kevin |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
What you need to do is first find out what the ADC is reading. This little program will display the ADC reading on your computer. The program editor has a simple terminal program that pops up with a DEBUG command in the PicAxe. Loop: readadc 1, b1 'put the adc value into variable b1 debug b1 'send the value of b1 to the PC pause 100 ' wait for .1 of a second goto Loop This will stream the adc data to your PC. Now connect the circuit to a adjustable power supply, and adjust it up to you max charge battery voltage, where you want the dummy load to be switch on, say 14.5 volts. Note down the ADC reading. Then adjust the power supply down to you lowest voltage, the voltage you want the dummy load to switch off, like 12.5volts, and note down that reading. You now have your upper and lower adc limits for your controller. Next you need to write the controller program, but I'll let you have a go at that. The good thing about the circuit you have is it could be used for other jobs if you no longer need it as a controller. I had a 08 set up as a pump controller, no longer needed, so I made a quick change to the PicAxe software and its now controls my garden lights when it gets dark. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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