MAX712-MAX713.pdf (228713Bytes)
Evaluation_kit.JPG (138084Bytes)
Pin_configuration_Max712.JPG (31564Bytes)
Typical_Operating_Circuit.JPG (48867Bytes)
MAX713SWEVKIT.pdf (65323Bytes)
MAX713_EV_Pin_out.png (69233Bytes)
18/02/2010
Well here it is!! My attemps at building my own battery charger using a sample of the max712, here is the original post that inspired me, https://www.robotshop.com/letsmakerobots/node/9272 and special thanks to ezekiel181 !!!
Although I will build a prototype on a breadboard just to test I have already started drowing a circuit using diptrace. The final version will be a programmable battery charger using a picaxe 40x2, a keypad from Sprkfun to set the outputs and an LCD to display remaining time, elapsed time and the
Check list:
- Gather electrical components for the breadboard prototype
- Finish designing pcb with all corrections discovered from prototyping.
- Build prototype using all components of finished design (relays, keypad ...)
- Find a suitable power source ( laptop supply from dealextream maybe)
- Coding to understand keyboard input, do necessary calculations, set relays to correct position, display info on LCD.
Parts list:
- 12 or maybe 6 relays depending on how they are configured
- Blocking diode
- 1 external power PNP transistor
- 3 resistors( well thats what the datasheet says but I clearly see 5 in the diagram)
- 3 capacitors ( same as before, I see 5 in the typical operating circuit)
- A keypad to input info
- An LCD to display info
- A picaxe to drive set the relays depending on cell number, fast charge time...
Well the only bit of work I can put up is the box I am planning to put this all in, it may seem a bit large but this way the laptop power supply, keypad, LCD will all fit in perfectly!
The phones is there for size reference.
19/02/2010
Well my first idea on how to control the connections of pgm0,pgm1,pgm2,pgm3 was by using transistors as a switch, but since I don’t know how much current and in which direction it would be travelling meant that I would be safer off using relays.
I still need to do some more research to get some points strait but for now I am pretty optimist on this project.
There has been a change in my plans, voodoobot suggested using one of these http://www.sparkfun.com/commerce/product_info.php?products_id=9117 , which does seem like an interesting option, 1 of these with the select option would allow me to set all the needed variables, it would also be useful because it only requires 2 pins instead of the 7 that the keypad require. There is only 1 inconvenience, the coding, I have absolutely no idea how to read or even count the pulses, sure, a post here on LMR would helpJ but, since I have 2 samples might consider that part for my second battery charger.
Well know for the work;
For this I will need to input variables via the keypad into the picaxe, have it do a few simple calculations then have it set its outputs high or low to set the relays. The problems come when dealing with R1, a resistance that need to be changed depending on the batteries being charged, to solve this I have 3 possible solutions; 1 use a variable resistance condoled by the picaxe, 2 use a variable resistance that I will adjust by hand, 3 use a 8mA current limiting diode (from the max713 ev kit diagram)
