Clarification of the powersupply

[maca404]

Hi

First up thanks for a great project and releasing all this free of charge. I am currently building a hh rev4 and everything is going great. Just trying to get my head around some theories involved. The power supply is puzzling me a bit Ic1 is setup as a voltage doubler yet in the docs it says you should see +12v coming from ic1 to ic2 pin 3, the bit that confuses me is if its double shouldn't it be +24v. The only thing I can figure as it says its an inverting chip does that mean I have a +12 and a -12 supply which I know if I measured between them I would get +24v ?. Also when testing if I put the - probe of the DMM on the positive terminal of the 12v source and then the + probe on ic1 pin 2 should I see +12v and on pin 1 of ic2 I should see +5v ?

Sorry about what probably seems a silly question but I have never dealt with a 7660 chip before and im trying to get my head around it.

[habitbraker]

Measure voltage between -VB and IC2 pin 3

[maca404]

Measure voltage between -VB and IC2 pin 3

I guess the thing which is confusing me then is, why is v+ considered ground as stated in the document ? And also how is it this is a voltage doubler when the build document states its output should be roughly the same as the battery voltage ?. I did read the data sheet but I still just can seem to grasp the concept.

[Qiaozhi]

Hi

First up thanks for a great project and releasing all this free of charge. I am currently building a hh rev4 and everything is going great. Just trying to get my head around some theories involved. The power supply is puzzling me a bit Ic1 is setup as a voltage doubler yet in the docs it says you should see +12v coming from ic1 to ic2 pin 3, the bit that confuses me is if its double shouldn't it be +24v. The only thing I can figure as it says its an inverting chip does that mean I have a +12 and a -12 supply which I know if I measured between them I would get +24v ?. Also when testing if I put the - probe of the DMM on the positive terminal of the 12v source and then the + probe on ic1 pin 2 should I see +12v and on pin 1 of ic2 I should see +5v ?

Sorry about what probably seems a silly question but I have never dealt with a 7660 chip before and im trying to get my head around it.

The article is a little misleading. In theory (using the positive terminal of the battery as 0V) the voltage at IC1 pin 2 should be +12V. The "voltage doubling" only occurs if you measure relative to the negative terminal. In practice the voltage at pin 2 will be less than 12V, and could actually be much lower, depending on whether you decided to externally clock the 7660 or not. The important point is that it must be high enough to drive the 78L05 regulator (IC2) to provide the +5V supply. If the +5V supply is ok, you can move on to the next step.

[maca404]

OK, Just found a data sheet which explains far more clearly that the Ic actually charges a cap, and then the supply voltage and the cap voltage are applied through a diode giving you in affect a doubling. Hopefully thats it.