powering a 555 off mains

I'd like to make a 555 PWM speed controller to drive a mosfet and switch a 240V DC motor that normally runs off a TRIAC circuit fed into a bridge rectifier. The TRIAC controller normally is set up to output 240V max from the

340V rectified mains and while it works ok has no low down torque and outputs an awful lot of RF interference.

My main query is this: what's a simple effective way to generate the 12V DC or so to power a 555 IC off 340V DC?. I was mainly considering a power resistor/zener combination.

Reply to
Mark Harriss
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On Tue, 29 May 2007 22:30:13 +1000, Mark Harriss put finger to keyboard and composed:

That's how it's done in cheap household appliances, eg timers, toasters.

See

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- Franc Zabkar

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Reply to
Franc Zabkar

"Mark Harriss"

** Totally nuts idea.

** ROTFL

So what fool's magic will make using a MOSFET any different ??

Go have a look at a *half wave* SCR drill speed control - low speed torque is kept high by the use of back emf induced feedback of the firing phase.

Many kits designs have been published by EA and SC.

...... Phil

Reply to
Phil Allison

On Tue, 29 May 2007 22:30:13 +1000, Mark Harriss put finger to keyboard and composed:

Is this a treadmill application? Just curious ...

- Franc Zabkar

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Reply to
Franc Zabkar

Production gemstone faceting machines Frank, the speed controller sits in an earthed, cast metal box and they've been made for 40 odd years using triacs but the lack of low end speed and the bad interference as well as some false triggering problems when you have more than one unit on the same powerpoint makes me want to evaluate a slightly more recent design principle.

Reply to
Mark Harriss

I wondered if my post would bring you flapping out of the woodwork of Nostradamus' coffin.

Reply to
Mark Harriss

Hey Franc Did ya get that lighting cct sorted ??

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Cheers .......... Rheilly P
Reply to
Rheilly Phoull

On Wed, 30 May 2007 17:54:13 +0800, "Rheilly Phoull" put finger to keyboard and composed:

If you're referring to that recent continuation of a very old thread (22 Feb 2007), then the OP with the problem was Nick Hobbs, not me.

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- Franc Zabkar

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Reply to
Franc Zabkar

On Wed, 30 May 2007 19:01:29 +1000, Mark Harriss put finger to keyboard and composed:

FWIW, I see used MOSFET based (?) PWM treadmill DC motor controllers (120V) on Ebay for US$60.

- Franc Zabkar

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Reply to
Franc Zabkar

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