Hi all:

>>Hi Conor, here SET:
>>Some time ago I made an EPROM programmer for PC and I see this problem, you
>>can:
>>1) Use an external power supply attached to your board.
>>2) Use an step-up converter (DC-DC), for example a 78S40 switching chip.
>>3) Use a simple voltage doubler with 2 diodes and 2 capacitors, this solution
>>is the simplest but you'll be loosing the 70% of the power, that's isn't a
>>problem in a PC where the 12V supply can drain 8 A (Not to one slot!!).
>>
>>bye SET.
>>
>Option #3 is not an option...   A voltage doubler like this works on AC, not
 DC!
>...
>Robert
  Robert, you don't need AC you only need an square wave, you can generate the
square wave with the PIC and amplify it with a transistor, you can generate the
square wave with 2 transistors or a 555 or a 4093 or any thing that you want.
  I used this trick to handle a MOSFET in a car, for this task I needed at
least 8 V over the battery voltage, I solved this with an output of the PIC at
5KHz driving a transistor with 120mA of Ic (when satured) and 2 electrolitic
capacitor plus 2 diodes, the output is just the double of the battery and drops
4 V if you charge it with 40mA.
  That's all, is cheap but ineficient in terms of transfered energy, but who
cares with a 12 V 8 A power source?

bye SET

********************************************************************************
Salvador Eduardo Tropea (SET) - salvador@inti.edu.ar
Work: INTI (National Institute of Industrial Technology) Sector: ICE
(Electronic Control & Instrumentation)
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