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G8MNY  > TECH     16.05.19 08:00l 71 Lines 3122 Bytes #6 (0) @ WW
BID : 5028_GB7CIP
Subj: Economy Turn ON Timer
Sent: 190516/0553Z @:GB7CIP.#32.GBR.EURO #:5028 [Caterham Surrey GBR] $:5028_GB

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By G8MNY                                      (Correction Feb 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

I was asked to develop a circuit that would press the washing machine on button
after midnight, to use the cheaper electricity. This circuit was needed as the
new fangled micro processor model would not work from a plug timer like the old
one did with a clockwork control.

This is what I came up with...

        Xrated                         | Double insulated
         u47      1N4006  +            | Lead to machine            Wired
from   ³    _³_  ³      ³  10u  ³      |          ÚÄÄÁÄÄ¿     \___> washing
timer  1M   /_\ ===1u5  ³  250v ³+     |       48VÀÄÄÂÄÄÙ     o     machine's
       ³  1N4³   ³250V 330k    ===4u7  |       Dil   ³15k     ³     TAC ON
       ³  006³   ³      ³       ³ 63v  |      Relay  ³        ÀÄÄÄ> Switch
     Built in an old plug top PSU case |

A 24 hour timer is still used to control the adjacent tumble dryer & it is set
to start at 01:00 AM & stop at 21:00 if washing is preloaded ready. So I used
this timer system to initiate a short ON pulse to the permanently powered
washing machine's ON button.

When playing with wiring to micro processors stray signal pickup & spikes must
be avoided so the contacts of a small high voltage relay is used to mimic
pressing the on button. Although an opto isolator would work just as well in
many circuits, you have to know which round to wire it to the TAC switch etc.

The relay is mounted very near the switch ensure there is no stray signals on
the wires.

On applying mains, the voltage ratio attenuator of the mains X rated cap (250V
50Hz) & the 1u5 (250V DC) cap reduce the 230V mains by 4. The 2 diodes form a
voltage doubler to give about 120V DC peak. This is fed through the 10uF 250V
electrolytic to the low current 48V relay which operates. (N.B. some relays
have internal back emf diode, & must polarity correct!) After about 2 seconds
the 10uF charges up & the relay releases.

The 4u7 63V electrolytic just stops the relay buzzing with the 50Hz pulses.

The 1M across the mains discharges the u47 to stop shocks when the plug is
removed. The 330k discharges the 10uF in a minute or so to enable a retrigger
for testing. (not needed over 24hr!)

The power consumption is very low at 100mW, much lower than the possibly safer
plug top PSU & a timer circuit design that would take about 4W.

(P.S. Most of the components you will find in a scrap TV/SMPSU)

See my bul on "Saveplug Motor Economiser".

Why don't U send an interesting bul?

73 de John G8MNY @ GB7CIP

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