Are the BoMs really the same, except for the regulator itself?
-marc
I should probably clarify…
Ordered one 3.3vdc and one 5.0vdc breadboard power supply. I know from the product description that the boards will both have 5vdc on the silkscreen – no problem. But the resistors/capacitors for both boards are also the same – although the regulator is different (one 7805 on LM317T).
Is this just a clever design where the LM317T’s variable output is pegged at 3.3vdc based on the resitor/capacitor network and they just happen to be adequate for the 7805’s needs too?
-marc
I didn’t design that board, but we don’t normally use LM317’s for regulating. Where did you see that? I can’t find that part number in the description.
Pete
I like those breadboard power supplies; they’re pretty cool. I have a similar one that came with an electronics book.
Any chance on making one that’s switchable between 5V and 3V? Or throwing a pot on there to make it adjustable?
Mike
Pete-O:
I didn’t design that board, but we don’t normally use LM317’s for regulating. Where did you see that? I can’t find that part number in the description.Pete
The part number isn’t on the description. It’s on the regulator. I have what are supposedly one 3.3vdc and one 5.0vdc unit that I recently ordered and am trying to establish I’ve been misshipped two 5.0vdc units before I build.
The LM317T is variable output, and can actually do both output voltages.
-marc
Hummm, ok well is your bare pcb the same as the one online?
If so there are no resistors to make the referance voltage so i would not have expected the 317 to be used!
Further more with the low end power supply (6V) and the series diode (0.7V drop) u get 5.3V the lm317 i think needs about 1.2V above output to work efficiently.
So using the lm317 should only be with 3.3V applications! I would expect a low drop out variant of the 7805 for the 5V type as its much cheaper.
Just had a look on the sparkfun shopping store and have found they have the LM7805 and LM7833, 5V and 3V regulators.
With my earlier comment, the LM7805 should have a 2V drop out, so supply should be >7V…
The 3.3V one is 2V too making a minimum input voltage of 5.3V
As a follow-up: I followed the traces on the board and nothing is connected to the centre pin – therefore no reference voltage. So this definitely is a fulfillment problem.
-marc
Ok, so there is the possibilty sparkfun sent a LM317 instead of the LM7833 or LM7805
Or whoever does their fulfillment. It’s also quite easy to mistake one regulator for another 
The PCB is the bit that’s important to me – I can replace the regulator with one bought at my local electronics store.
But if someone from Sparkfun can investigate, it might stop others getitng a regulator that will only generate 1.25vdc
-marc
Hey Guys!
:oops:
Please email Jeff at fun @ sparkfun.com and call him many icky names. He stuffed the kits with the wrong regulator. We’d be happy to send you a free LM7833 regulator.
The 5V kits are correct.
The 3.3V kits were shipped with the wrong regulator up until I noticed them on the 15th or 16th (last week).
Really really sorry,
-Nathan
PS - Where do we find customers like you guys?! Any other customers at any other company would be calling and yelling at us. You guys sit down and have a discussion about PCB traces and the inner-karma of a variable LM317 regulator! Thanks so much!
Heh…the reason we like Sparkfun is the curious minds we have
As a follow-up: Sparkfun added a free LM7833 to my recent order to rectify the problem and apologized for the error in an email and got a free LM317T to boot. Satisfactory end to a bit of a saga.
Oh, and Nathan confirmed that indeed the BoM for both the 5.0vdc and 3.3vdc breadboard power supply kits is indeed the same apart from the regulator itself.
-marc