5V-regulator

[AndreyB]

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

[AndreyB]

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

[kb1gtt]

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.

[AndreyB]

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.

[kb1gtt]

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.

[AndreyB]

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

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?

[kb1gtt]

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?

[AndreyB]

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?

[kb1gtt]

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.