Anyone who has the DRV8825 stepperdrivers? Run nicely and quiet and all but when cranking up the current to just 1.5A they go into overheating shutdown and when at 1A i loose steps at least at the Y axis.
Anyone activcooling these?
Just checking… you’re using the right equation to calculate current/vref, right? All else being equal, an 8825 should be able to handle a higher current than a 4988.
What heatsinks do you have on them?
@Ryan_Carlyle well current should be vref * 2 as far as i found. Setting it to 0.75V gets it to cook. There were aluminiumheatsinks packaged with the drivers.
Yeah, that should be right if these are Pololus or equivalent. You could doublecheck that the sense resistors are 0.1ohm to be sure that’s the right equation.
Unfortunately I don’t think I can be much more help than that… when I briefly ran Pololu 8825s I had them “upside down” in a Mightyboard so the heatsink was on the opposite side from the driver chip. You get better heat-shedding that way since the thermal via below the chip pumps heat into the PCB. A heatsink on top of the driver chip doesn’t actually accomplish all that much. Anyway, I had them at 1.2-1.3A or so without any issues or forced cooling, but again, Mightyboard-style drivers shed heat better.
FYI, I stopped running 8825s when I realized how much stepper rippling they cause on 24v systems or with low-inductance motors. They’re very sensitive to motor/PSU combo. That could be contributing to your skipped steps… 1A on a NEMA 17 should provide adequate torque for any normal-sized printer without excessive friction or acceleration settings.
@Ryan_Carlyle Thx you very much
i have the rather standard ramps 1.4 and 8825 setup, i currently have them at 1.2 - 1.35A (at around 1A i was skipping steps as well on faster prints) but i started out at ~1.4A and ran them for hours without any problems using this enclosure http://www.thingiverse.com/thing:761806 with a 50mm quiet fan. it’s perfect because it both helped wire management out of the ramps and the drivers are cooled.
you can try pointing an 80mm fan at them temporarily with some clip-on (lot’s of those on thingiverse) and see if it helps…
it was one of my first prints, so i never tried running them much without active cooling (barring the first few prints with that setup).
Thx to all. Well put my A4988 on again. Sad but there is no chance without active cooling… The A4988 seem to be the reliable option there…
It’s strange, because the 8825 has a lower RDSon (FET resistance) so it should be generating less heat at a particular current than the 4988.
@Ryan_Carlyle I agree, but it’s an issue with the standard stepstick design, not the DRV8825 itself on 24v systems.
I have patch-wired my DECAY pin to 5v, and now they run smoothly and silently at 24v with 0.5v vRef.
The stepstick design really needs a DECAY select jumper.
@Jason_McMullan Most people get angry hissing noises on 24v in fast decay mode. It’s very inconsistent whether your motor gets the audible subharmonics or not. I don’t know any way to predict it in advance (unlike the rippling, which I can simulate). But yes, fast decay does fix the position ripple issue if you don’t mind soldering a jumper onto SMD pins 
The underlying issue is all the 3d printer driver designers copying Pololu without doing any real engineering. Pololu sets their driver defaults for much higher inductance steppers than we run in 3d printers.
I’d personally rather we switch altogether to driver chips with better decay algorithms or adaptive decay, like the THB6128, a5984, or whatever else. The technology level in affordable stepper drivers has improved dramatically in the past 5 years. There’s no particularly good reason to keep using 4988s and 8825s at this point. (I really like integral SPI drivers like the TMC2660 on the Duet Wifi… but the Pololu-socket drivers still have some value for legacy hardware support.)
@Ryan_Carlyle I wonder if the angry hissing as a holding-z issue with Cartesians.
My delta only hisses when it stops at certain points and certain loads. Otherwise it’s quiet
@Jason_McMullan yep that’s it. Not all microsteps hiss, and those that do all hiss with different sounds, so as long as every motor is constantly moving it won’t be noticeable. Which only happens with deltas.