Step motor drive for flame effect fire.

[expat]

I have a friend that has a Dimplex Flame effect electric fire.
The flame effect has gone wrong.
It consists of a Tinsel rod driven by a slow speed motor.

The motor in question happens to be a 12v step motor with gear reduction (64 to 1) like this:
http://www.robotshop.com/ca/en/seeedstud...gn=GoogleCanada

The problem is, it's not the motor that happens to be the problem, it appears to be the driver!

Now, step motors were all new to me before a looked into this, It seems a little over engineered. But id I were to get a new step motor driver, what type of driver would simply drive the motor round and round at about 4 rpm?
Thanks.

Dimplex want over $200 for a replacement driver!!

 

[djb]

Post a picture of the circuit board and assembly.

Many simple stepper motor drivers use the ULN2003 chip as the output driver. These are cheap and readily available. It's rare for them to fail, but this may be severe service.

 

[expat]

Originally Posted By: djb
Post a picture of the circuit board and assembly.

Many simple stepper motor drivers use the ULN2003 chip as the output driver. These are cheap and readily available. It's rare for them to fail, but this may be severe service.



Sorry, it's not possible to take a picture of the old circuit board right now (and would be a bit of a pain to do anyway.

I'm beginning to think a 110v low speed gear motor might be a simpler solution anyway.
I wonder why they used a Stepper and Driver in the first place?

 

[expat]

Originally Posted By: djb
Post a picture of the circuit board and assembly.

Many simple stepper motor drivers use the ULN2003 chip as the output driver. These are cheap and readily available. It's rare for them to fail, but this may be severe service.



I just noticed that I actually have a ULN2003 circuit board that came with the motor.
But it was no-way like the board that was in the fire.
My guess is the ULN2003 would need something to drive it?

 

[PandaBear]

From what I remember during my time working with step motor, you cannot just have it spin round and round as it is without some sort of controller signal change going into the driver. If your driver is going bad and you only want the motor to spin without worrying about the speed or stability, anything will work.

If the motor is fine (i.e. not overheated and demagnetized, or cooked the insulation on the coils, etc), and your controller is still fine and only the driver is bad, you can replace just the driver chips with the same ones with soldering iron. I've seen some that cost $1 for 2 channels and powerful enough to drive a printer motor.


"At around 4rpm" is the hard part and why they use the step motor, and it is already easy compare to using a servo motor with encoder and more complex control system.

 

[PandaBear]

Originally Posted By: expat
Originally Posted By: djb
Post a picture of the circuit board and assembly.

Many simple stepper motor drivers use the ULN2003 chip as the output driver. These are cheap and readily available. It's rare for them to fail, but this may be severe service.



I just noticed that I actually have a ULN2003 circuit board that came with the motor.
But it was no-way like the board that was in the fire.
My guess is the ULN2003 would need something to drive it?


It is driven by a logic chip run with a clock that periodically change pattern, do you know if your existing controller is good or not?

You may be able to wire out the pins from your original board to the new driver board you have and see if it works (it would if it is like you said only the driver chip that died).