MakerFarm 8" i3v Prusa build by Printbus

[TopJimmyCooks]

I have a 12V only power supply but I'm going to add 5V power, possibly using a cell phone car charger or similar, to be able to run ABL without USB connection. might try a $5 UBEC instead. I'm also interested in doing the raspberry/wifi octopi setup and will need 5V for that.

[AbuMaia]

I would have thought a need for a secondary power supply would have been mentioned somewhere, or do all the kit makers assume we'd be using PC power supplies?

[TopJimmyCooks]

PC supplies seem to be recommended by Makerfarm and other kit companies. However, right out of the box there's nothing to connect 5V to. I went with a 12V power supply so it could be mounted on the printer. Now, as I'm printing more stuff, and print longer prints with the SD card, the onboard 5V starts to be more important.

[printbus]

If I wanted to add 5v for a Pi or ABL servo, I'd do like TopJimmyCooks and use a BEC or other regulator running off of 12V so I don't need to add another AC plug.

AbuMaia, by kit makers are you referring to people like MakerFarm? The printer kit as delivered works fine on just a single 12V supply. It's adding stuff onto their printer that is driving the possible need for an additional power supply or regulator, and there's no way they can predict what people are going to try to add.

[printbus]

Also, let's not panic here. I think I'm the first raising the possible theoretical issue of running an ABL servo on a standalone printer, and I don't even have ABL implemented. We need feedback from people with ABL experience on whether they've seen ABL (or the entire Arduino electronics suite) ever acting up when standalone.

The symptom of the MEGA2560 voltage regulator going into thermal protection is that the 5V gets shut off until the regulator cools off, and then the regulator will turn back on. That should be a pretty noticeable symptom, and I don't recall hearing anyone describing their printer going dead momentarily.

[AbuMaia]

I run my printer entirely standalone, printing off of SD, except when I need to adjust something or update the firmware. I am yet to have any problems with the ABL servo, apart from it moving seemingly randomly when I had a LM7805C attached to it per some people's advice. Once I removed the regulator, I had no more problems.

http://forums.reprap.org/read.php?15...979#msg-286979

[printbus]

http://forums.reprap.org/read.php?15...979#msg-286979

OK, at least now we know I'm NOT the first to raise concerns regarding power for a bed leveling servo.

[AbuMaia]

I do find it odd that my experience seems to be the opposite of many others. My servo works just fine plugged into RAMPS, but when I add a 7805 to give it separate 5v, it goes crazy.

[printbus]

I do find it odd that my experience seems to be the opposite of many others. My servo works just fine plugged into RAMPS, but when I add a 7805 to give it separate 5v, it goes crazy.

Well, the reprap thread you linked to talks about the same thing I've been saying - not all servos are the same. You could basically just be lucky with the servo you have not drawing a lot, or you don't put much of a mechanical load on it, never stall it (ie, servo is not put into a situation where it mechanically can't move), and the MEGA2560 regulator has a chance to cool off in between servo moves.

On the 7805, did you include any capacitors on the input and output pins? If not, that could be part of why it didn't work out. A larger capacitor on the input would help sustain the input voltage to the regulator during current surges, and a smaller capacitor on the output helps keep the regulator stable with the inductance of wiring connected to it. What I remember from reading countless datasheets and application guides over the years is that the input capacitor is generally required if you're more than a couple of inches from the power source, and the output capacitor is generally viewed as always required.

[AbuMaia]

On the 7805, did you include any capacitors on the input and output pins?

No. I had the Input leg inside the + connection on RAMPS, clamped together with the + wire from the power supply. Same with the ground leg and - wire. Output was sent off to some pins I've forgotten, connected by a wire with a jumper on the end.

Is something like this what you were talking about? http://www.amazon.com/LM7805-Termina.../dp/B00NCKUWE4