Direction of DRV8825 stepper motor driver / Rumba power

Hello, I bought a rumba board with DRV8825 stepper motor drivers and Im not sure which way the driver goes. Do I face the IC side closer to the molex connector or aways ?

Aslo, do I need to connect both main and heatbed power supply or will connecting main only do ?

I haven't used a Rumba in years (upgraded to a Smoothie), but perhaps this page will help:
[reprap.org]

Just in case you have a Delta: it's not recommended to use 1/32 microstepping with Delta printers (causes 2x the stepping load on the microcontroller), or graphical display.

Also, depending on your motors and voltage you may have some issues with missed microsteps with the DRV8825 drivers. This shows up as a repeating pattern in the perimeters. More info here.

Also, the DRV8825 drivers may make squealing noises. FYI: A4988 drivers are much better.

Try to always print from the SD card, much more reliable.

Hope that helps!

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
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someoneonly
Hello, I bought a rumba board with DRV8825 stepper motor drivers and Im not sure which way the driver goes. Do I face the IC side closer to the molex connector or aways ?

Aslo, do I need to connect both main and heatbed power supply or will connecting main only do ?

If you bought the original RUMBA made by Reprapdiscount with the matching stepper drivers the potentiometer on the drivers faces away from the molex connectors.

This is the diagramm that will help you.
[reprap.org]
Here you can see which pins of the driver belong where.

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Paul Wanamaker
I haven't used a Rumba in years (upgraded to a Smoothie), but perhaps this page will help:
[reprap.org]

Just in case you have a Delta: it's not recommended to use 1/32 microstepping with Delta printers (causes 2x the stepping load on the microcontroller), or graphical display.

Also, depending on your motors and voltage you may have some issues with missed microsteps with the DRV8825 drivers. This shows up as a repeating pattern in the perimeters. More info here.

Also, the DRV8825 drivers may make squealing noises. FYI: A4988 drivers are much better.

Try to always print from the SD card, much more reliable.

Hope that helps!

Some specs as far as I know from the kit
Act-Motor.com 1.8degrees 1.7A which might be 2.8mH (model number not found)
Power supply 12V 17A

The shop I bought from left out 2 drivers so I will need to buy some more. Do you think that I could run DRV8825 drivers for the extruders and A4988 drivers for the xyz axis(to save cost) ? Or should I just replace all drivers by A4988 drivers ?

I am pretty new to this but from what I understand the microstepping is put into prusa caculator and only used for steps per mm right ?

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Srek

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someoneonly
Hello, I bought a rumba board with DRV8825 stepper motor drivers and Im not sure which way the driver goes. Do I face the IC side closer to the molex connector or aways ?

Aslo, do I need to connect both main and heatbed power supply or will connecting main only do ?

If you bought the original RUMBA made by Reprapdiscount with the matching stepper drivers the potentiometer on the drivers faces away from the molex connectors.

This is the diagramm that will help you.
[reprap.org]
Here you can see which pins of the driver belong where.

Thanks, couldnt find this diagram anywhere , it really helps out alot.

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someoneonly
The shop I bought from left out 2 drivers so I will need to buy some more. Do you think that I could run DRV8825 drivers for the extruders and A4988 drivers for the xyz axis(to save cost) ? Or should I just replace all drivers by A4988 drivers ?

I don't see why not. You'll be much happier with the A4988 drivers runing XYZ, and the DRV8825 will have less issues with the extruder.

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Someoneonly
I am pretty new to this but from what I understand the microstepping is put into prusa caculator and only used for steps per mm right ?

Yes, that's correct.

Just curious, I can wire up my meanwell 12v 17a directly to the board right ? I have looked around the place for similar power supply wiring but they all seem to wire it directly.

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someoneonly
Just curious, I can wire up my meanwell 12v 17a directly to the board right ? I have looked around the place for similar power supply wiring but they all seem to wire it directly.

Yes, if that is a standard power supply, then you will wire as shown on the bottom of the diagram.

Ok thanks for all your help,but I am not sure why you can wire extruder fans(eg E3D fan) and boards with lower current value to a higher current value power supply XD looked around but all I see is complicated explanations.

Is just the same way you can plug-in different wattage lightbulbs into a wall socket, say
A one watt bulb or 100 W bulb. The 1W bulb has much higher resistance so it draws less current.
So each type of thing that is plugged into the board is using only as much current as it needs and was designed for.
There are some components on the board for example the processor chip that require a lower voltage. There is a voltage regulator that steps down the voltage for those components.

I believe that board will allow you to use a different voltage power supply for the heated bed.
You can use a higher voltage for the main board too but only with great care as the fans will blow if proper jumpers are not set, etc.

Okay, Thanks for the clarification.Somehow I always thought that if either the current or voltage is too high, the component is gonna burn out instantly.

So the 5A for the board and the 11A for the heated bed printed there are only general guidelines for the components loaded under normal/average load and it can actually take higher current ? I am slightly puzzled because the voltage is 12v-35v whereas theres no range for the current.

Yes, you can use a higher current power supply, and that is in fact the best way to go.
A power supply is rated in Watts which is Volts * Amps.
If you had an actual constant load of 1000w, and used a 1000w power supply, then it would always be running at 100% capacity - it's components would run hot and it would fail earlier. Sor for a 1000w load you would want a 1400w power supply, etc.

There is a direct relationship between voltage, current, and resistance. In electronics this is known as Ohms law.
In a hot end that is rated at a higher wattage there will be lower resistance - thicker or shorter - internal windings in the heater cartridge so it will pass higher current (amperage).

The voltage rating on your board 12-35 volts means that you can supply any DC voltage in that range.
At a higher voltage:
- The voltage regulators that drop the voltage for the processor and 12v fans will work just a bit harder (and get hotter).
- The higher voltage will be passed to the hot end, heated bed, and stepper motors.
- The hot end and heat bed will heat faster and will be able to reach higher temperatures (more current flows at higher voltage).
- The stepper motors will be able to run at a higher speed.
- The stepper motors and stepper motor driver chips will get MUCH HOTTER. I ran my rumba at 28V, and had special heatsinks on the motor drivers and a high speed (loud) fan blowing on the controller, and it took a while to get the motor drivers adjusted so they did not overheat and do intermittent thermal resets. [edit: this was incorrect, I just had the drivers set to too high current when I first built my printer.]

If you run a Rumba at a higher voltage, you have to be very careful, as the fan output pins can also carry the higher voltage. I blew an expensive blower fan this way. There are jumpers that set the fan voltage I believe.

Edited 2 time(s). Last edit at 02/01/2016 12:36PM by Paul Wanamaker.

Wow, I learnt alot today thanks to you. This deserves to be stickied or placed somewhere on the wiki.

Glad to help.

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Paul Wanamaker
- The stepper motors and stepper motor driver chips will get MUCH HOTTER.

If that happens then I think your drivers are faulty, or the circuit that generates the voltage reference for them is badly designed. Increasing the supply voltage should make no perceptible difference to how hot the motors run, and only a small difference to how hot the drivers run.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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DC42
If that happens then I think your drivers are faulty, or the circuit that generates the voltage reference for them is badly designed. Increasing the supply voltage should make no perceptible difference to how hot the motors run, and only a small difference to how hot the drivers run.

You are correct, thank you.
I did have very very low inductance steppers, but I was mis-remembering - when I got a Smoothieboard and inquired about running it at higher voltage they recommended more cooling. Perhaps that was for the regulators only.