Electronic Speed Control - TDA1085

[bigegg]

Just come across a blog about motor speed control, and one of the comments mentioned a speed control chip called a TDA1085 which is used in washing machines to control the main motor.
It seems to me that a speed controller based on this will be cheaper than the 3ph>VFD route (assuming one doesn't already have a 3ph motor)

I haven't done any electronics for about 20 years - and back then, AC motor speed control was done with a Triac, and a PWM circuit - and was horrendously expensive (seem to remember about 4hrs wage for a triac!)

The TDA1085 is about a fiver, delivered - and since I already have about a dozen motors...

But, as I said, I haven't done any electronics for about 20 years - they were a compulsory part of my degree, I wasn't particularly interested, and I just scraped through

Can someone with a bit more knowledge explain what else I'd need to control a motor?

 

[rtbcomp]

Washing machine motors are "universal" ie they have field coils and a wound armature with a commutator and you could use pulse width modulation (PWM) to control the speed, but PWM would not work with an induction motor.

What machine are you looking at motorising?

 

[bigegg]

My new holbrook 5c lathe. No motor fitted at the moment, but I have several universal motors.

Actually, I have an induction motor as well (on my pillar drill at the moment), but specifically looking at a universal motor + TDA1085 IC

 

[Sidewinder]

PWM WILL work with an induction motor, it just has to be done right!

 

[DanielW]

Whats the voltage of the motor?

 

[bigegg]

240v

 

[DanielW]

240v

Well thats put the mockers on it then.

I was going to suggest theres a treadmill on ebay for £20 spares or repair,these motors are 180v DC and got a lot of umph! and the controller is a variable one.

 

[normspanners]

Washing machine motors are "universal" ie they have field coils and a wound armature with a commutator and you could use pulse width modulation (PWM) to control the speed, but PWM would not work with an induction motor.

What machine are you looking at motorising?

A lot of washing machines now use 3ph induction motors I have repaired my hoover and fitted a new control chip, they rectify the mains, then produce 3 ph in the same fashion as a vfd but there is a lot of circuitry with logic programable chips etc to control the main chip which was mounted to a large heat sink but with no heat sink compound needless to say the new chip went on with compound and has worked fine since.
hoover wanted £260 for the panel!!, the new chip £23 from farnell, I even got a spare board off the bay and modded that ready.

 

[bigegg]

Well thats put the mockers on it then.

I was going to suggest theres a treadmill on ebay for £20 spares or repair,these motors are 180v DC and got a lot of umph! and the controller is a variable one.

I like that idea - I have used treadmill motors in the past.

As I said though, was hoping to build a generic speed controller which could be used for a range of projects, and be useful for people on here, rather than just a one-off project.