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G8MNY > TECH 03.01.03 18:07l 38 Lines 1669 Bytes #999 (0) @ WW
BID : 36279_GB7CIP
Read: GUEST OE7FMI
Subj: SCR Drill Speed Controller
Path: DB0MRW<OK0PPL<RZ6HXA<SP7MGD<GB7YKS<GB7PZT<GB7MAX<GB7COV<GB7COV<GB7CIP
Sent: 030103/1323Z @:GB7CIP.#32.GBR.EU #:36279 [Caterham] $:36279_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY
Here is a simple circuit I use for a pillar drill. It suffers from speed
variation due to mains fluctuations. And is only suited for AC/DC (eg brush)
motors, and must not be used on AC Induction motors!
D1 D2
Live ---Motor----------!>!------!>!-------------
with ! ! !
Suppression ! --- 100K
! SCR \ / Diac !
Full \ --- !>! !
Power ! ! \--220R-! !------!
! ! !<! ! 10K Multi
! ! === ! Turn
! ! C ! !
Neutral ----------------------------------------
My drill motor was only 500 Watt so...
D1 is 1N5403 (50A peak), D2 is 1N4003
C is a 0.1uF (63v)
DIAC any 20v device (higher voltage = less control at low RPM.)
220R is optional depending on the sensitivity of the SCR.
SCR is a 3A 400V device (50A peak) it can be a Triac as D1 inhibits wrong
way conduction. (mine used to blow up until I added the diode.)
Switch shorts out controller for full Power.
Multi turn low speed control is a preset pot in my design.
This circuit attempts to put DC out to the motor 50 times a second, every other
half cycle (variable to half power mode). How much DC depends on the preset
setting & the motor back emf. Hence the power/torque has some feedback feature
unlike just phase control, & enables variable torque loads to be handled much
better, without dramatic RPM changes.
73 De John, G8MNY @ GB7CIP
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