rusefi.com

Another option for a power supply

https://svn.code.sf.net/p/rusefi/code/trunk/hardware/5V-regulator/
https://svn.code.sf.net/p/rusefi/code/trunk/hardware/5V-regulator/PWR_5V_linear.pdf

RV1001 is currently through-hole, is that because it needs to be 1/4W? Could it be implemented as two 0805 resistors?

Need a silkscreen mark for D1001

rv1001 is a multi turn POT which allows you to adjust the output voltage. Such that this can be a 3.3v, or a 5V. The SMT' POT's are usually single rotation and poor resolution.

kb1gtt wrote:rv1001 is a multi turn POT which allows you to adjust the output voltage. Such that this can be a 3.3v, or a 5V. The SMT' POT's are usually single rotation and poor resolution.

what is the value for 5v output? if I want fixed output, can I use 0805? sounds like an explanation is needed on the schematics

actually it would help to know a more common pair of these adjustment resistors since I probably do not have 240R. that's assuming changing R1006 changes output.

Ooops, D1 is missing as noted in this datasheet. http://datasheet.octopart.com/LM317MDTG-ON-Semiconductor-datasheet-512589.pdf I know it should be there, why I forgot to put it in is a blah. Any how it's kind of needed or you can damage the regulator. It's a fast transients reverse polarity thing.

The POT is $.040 from here http://www.sky-macau.com/Products/3296-Series-C165/3296W-3296-Series-High-Precision-Variable-Resistors-Potentiometer-Trimmer-102-1k-Ohm-P2633110656.html

For 5V output I would expect RV1001 can be replaced with 720 ohms. The current through it will be 5V / (240 + 720) = 5.2mA Then I expect (5.2mA^2) * 720 = 20mW. So yes an 0805 would work fine. It can probably be easily installed across the center pin, to either side pins of that POT.

Got myself some 240R and 715R (no 720R on digikey)

kb1gtt wrote:Ooops, D1 is missing as noted in this datasheet...I know it should be there, why I forgot to put it in is a blah. Any how it's kind of needed or you can damage the regulator.

Just to clarify: the semi-assembled board pictured before is NOT functional, I should not waste time finishing it?

What is the tolerance of the 715? Does it happen to measure 720? AKA 1% resistor 715*1.01 = 727.2 ohms. So a 1% might be 720 by luck.

I could find slightly different values for the 240 and 720 to make this land spot on. Should this be updated, adding D1 and changing the hard installed components slightly?

240 and 715 are both 1%. Can you commit updates schematics/pcb and I will try hacking the board with the extra diode.

By the way I suspect that I've used the same "Zener Diode 20V 20V0 20.0V 20.0 V 1W 1000mW DO-41" for both D1003 and D1002. D1002 says "Zener Diode 15V 1/2W 500mW 0.5W DO-35". Would it work? I guess these are different for a reason, but the values are so clooooose

By the way D1003 symbol shows just normal diode, not Zener?

On Q1001, it's only rated for 20V, the Q1002 is keeping a 200V spike clamped to 15V(diode) + 4.5V(MOSFET gate) or 19.5V which is below the 20V max of Q1002. So I expect that having D1002 at 24V instead of 15V is to high and would result in damage if you have a 200V surge. I'm not 100% sure why I had 30V noted next to Q1002, I think that was from a prior chip. The chip that's noted in there now is only 20V. I seem to recall that 30V at a higher current was hard to find, and to get more obtainable chips it changed from 30V to 20V. I just changed / committed this on the R0.2.

Also there is a 50uA adjust current that ends up changing the Vout equation slightly, and the 715 is actually better than 720 ohms. I added this calculation to the schematic.