I'm trying to figure out why I keep overheating and ruining wall wart power supplies. I am using a 12V 3A power supply to power the Adafruit Motor/Stepper Shield V2 which is driving two stepper motors (see attached spec sheet).
The stepper spec. sheet states that the motors draw 0.85A per phase (configured for bipolar not unipolar), and the shield can provide 1.2A per phase per motor, so I don't see any issue. Even if both motors are drawing 1.2A wouldn't a 3A power supply be sufficient?
That Amazon page has plenty of reviews panning the power supply: "Power supply cannot handle 2A, let alone the 1.6A my 12V LED string requires. Goes into over-current mode at 1A.". Another review states that it has a 1.5A fuse inside.
There are much better options for driving steppers than a motor shield like the one you linked. "RAMPS" shields with drivers included should be available on Amazon or eBay, and then you can use any power supply 12V-40V, like an old laptop power supply, and get better performance from your stepper motors without the worry of overheating them.
The modules that plug into these boards are available very widely; usually searching for "stepstick" will get you what you want. Pololu is kinda the authority as they created the originals which then were cloned by "everyone". Pololu has excellent documentation on their use.
When using these drivers, since they include current limiting, you can use any power supply up to ~35V (like an old laptop power supply). That's the big advantage of using drivers like these; you're not limited to the stepper rated voltage. You'll get more responsive (faster) action from your motors by using a higher voltage supply.
Normally.... if you are really running the supply at half the rated capacity.... then should be ok. If your supply gets hot... then it needs something to remove the heat.... eg. fan etc. Since you are using wallwart... then try using a BIGGER volume one..... one that handles more heat.
Or try a more substantial supply with larger power output capability.
You'd pay more for one in a case (which is necessary for mains supplies, but often you are already
building a project inside a case).
A small sealed plastic power-blob cannot dissipate enough heat to handle 36W, the supply you
selected was never going to be adequate, I doubt its even safe.
MarkT:
This is what a 36W power supply tends to look like:
Not to be too nitpicky but the 36W (3A) version is not what is pictured. That item is described as "3.6 x 2.6 x 1.7 inches". The pictured item looks like a 10A version or more.
Chagrin:
Not to be too nitpicky but the 36W (3A) version is not what is pictured. That item is described as "3.6 x 2.6 x 1.7 inches". The pictured item looks like a 10A version or more.
Yep. It was the thirty Amp version. They're all sort of the same in terms of a cage .... but some have bigger heat sink and/or fan.
MarkT:
A small sealed plastic power-blob cannot dissipate enough heat to handle 36W, the supply you
selected was never going to be adequate, I doubt its even safe.
I agree , even if it is safe for a resistive load, that can change when supplying inductive loads.
Although IME some just shut down when presented with such a load, (fortunately).
A motor has a higher power usage at start up, so if a motor spec says 1.2 Amp this means that it consumes 1.2 amp while running, but at the start up the amp peak can reach then 3.6 Amp for example.
Yes, but they need 'proper' supplies.
Many here seem to use wall warts which are not suitable for motor supplies.
Arduino kits have such supplies which work for small motors but are unsuitable for a lot of practical applications, as asked for by some builders.
Dece:
A motor has a higher power usage at start up, so if a motor spec says 1.2 Amp this means that it consumes 1.2 amp while running, but at the start up the amp peak can reach then 3.6 Amp for example.
Actually when power is first applied, there is minimum current as inductive kickback will not allow current flow.
As time goes by the current builds up to maximum based on the winding resistance 'give enough time'.
A normal motor has maximum current flow if you stall the motor.
[ Inductive kickback is when the current is abruptly halted, not when you connect power to an inductor.
Kickback happens because the dI/dt is very large, and voltage is proportional to dI/dt for an inductor.
When you first connect the V is the power supply voltage, ie modest and hence the dI/dt is modest too. ]
The comment about motors taking more current at startup is wrong for a quite different reason, namely
stepper motors are not DC motors and do not behave the same.
DC motors do draw large currents at startup (stall current) until the speed (and back EMF) builds up.
Steppers do not, they are completely different. Steppers basically take the same current all
the time (well up to the top of the speed range, where it drops off).
MarkT:
[ DC motors do draw large currents at startup (stall current) until the speed (and back EMF) builds up.
Steppers do not, they are completely different. Steppers basically take the same current all the time (well up to the top of the speed range, where it drops off).
It should depend on how the stepper is driven. If driven with a current limiting circuit or a controlled current circuit ... then yep.... the current will stay under a desired value.
MarkT:
The comment about motors taking more current at startup is wrong for a quite different reason, namely
stepper motors are not DC motors and do not behave the same.
My bad , that will tell me to read the posts properly.