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Old 10-07-2022, 04:55 AM   #1
Cornboats
Dave
 
Join Date: Oct 2010
City & State: Worcestershire
My Country: United Kingdom
Line Voltage: 240v 50HZ
I'm a: Knowledge Seeker
Posts: 152
Default Help reading this electrical schematic

I'd like to make a motor speed controller on an ex brush universal washing machine motor.
The motor runs for too fast so I'd like to reduce the revs down into the 10s. I've bought several motor controllers off Ebay/Amazon but the 240v version doesn't maintain the motor at low speed under load at constantrevs. The DC version I bought was good at low revs but I turned the unit on without turning the control potentiometer down first. This has blown something on the board and the fets/triacs aren't marked( Chinese) so I can't replace the obvious. I found this drawing on line and decided its better to make up my own. Trouble is I can't understand some of the notes on the drawing. Can someone talk me thro this?
EG. What are PAD 1,2,3,4,6&7 . Also theres no low voltage rail so everything seems to run off 240v- Is that right?
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Old 10-17-2022, 10:40 AM   #2
alfatv
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Default Re: Help reading this electrical schematic

Low voltage rail is generated by D2, D1, C1, C2.
Why don't you try light dimmer?
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Old 10-17-2022, 12:13 PM   #3
redwire
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Default Re: Help reading this electrical schematic

OP's TDA1085 circuit has constant speed control. It uses feedback from a tachogenerator and/or motor current to stop the motor speed from sagging under load, like a dimmer would do.
Same circuit as a wood planer, I'd have to dig for it. The IC gets low voltage DC power from mains derived through the zener D2 and dropping resistor R20. That schematic has some mistakes in it.

If it's some no-name chinese special, I would expect the triacs to be junk and the IC questionable quality. But they are easy to replace.
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Old 10-18-2022, 02:41 AM   #4
Cornboats
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Join Date: Oct 2010
City & State: Worcestershire
My Country: United Kingdom
Line Voltage: 240v 50HZ
I'm a: Knowledge Seeker
Posts: 152
Default Re: Help reading this electrical schematic

Thanks to both your replies. I'm going to build my own controller based on the TDA 1085 as the ex washing motor I want to re purpose already has a tacho fitted on the end.
I haven't got the knowledge to design from scratch but can build from a drawing.
I'll search online to see if there are any I can use.
Many thanks for taking the trouble to reply.
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