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Uniselector mini project.

Hi all,

I would like to use a uniselector (got) to step to its next position upon connection to a mains supply (through 'X' circuitry). This will probably be at one_per_day time intervals.

Ideally said circuitry would consume as little energy itself as possible.

What I'm actually trying to do is 'cycle' an intelligent low current (.5A) but quite expensive charger to a range of smallish 12V lead acid batteries. Once each battery is actually charged (probably elsewhere) it will be kept topped up by said project applying said charger once every Y days (where Y could be 25 as I think it's a 25 way selector).

I could use (make) a 240 ac to 50V DC PSU (assuming the uniselector was designed to run at that) and then create a suitably long one shot pulse on power-up (charge cap?). I could probably even just use one mains digital time switch, energising the uniselector 'step' cct for one minute, again via a suitable charge cap (so the coil isn't left energised for longer than needed)?

Ideally though both the charger and the stepper sides would be power cycled at the same time (to ensure the charger was reset). Or the charger de-powered when the selector is pulsed (so the selector isn't actually switching the charge current).

Ideas welcome please. ;-)

Cheers, T i m

Reply to
T i m
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Use a DC supply to run it, and (say) 2200uf electrolytic in series. This will hold it in for a couple of seconds upon power up. If it is not long enough, use a larger value cap. It would be a good idea to put a diode across the coil, with the K (stripe) to the positive to prevent back EMF from the coil possibly damaging the capacitor over time.

Note that this will pulse the coil once every time you turn on the power, it will not pulse again until the power is turned off and on again.

I have used this method in the past with relays to provide a power on delay and it has worked well for over 10 years.

Reply to
KR

Would you make summat (transformer, bridge rec, cap) or just get a wall wart sorta thing?

Understood. My original thought (to keep the residual current down) was to just half_wave_rectify the mains and use that with the cap idea as once up to potential there shouldn't be much in the way of current (if both charger and this circuit were powered from the same mains timer etc). It's just the coil could initially have more than 50V across it (zener?) and I'm not sure how it would cope with un smoothed half wave rectified current? How much current do transformers draw when there is little load?

Understood.

Yup, exactly what's needed. As long as the cct can reset quickly (so that would be down to a 'bleed' resistor across the cap presumably) then the timer could just provide a 1 min off time. If not I guess 15+ mins (as per the mechanical timers) may be required

That's another thought, slugging the start up of the charger to after the selector has stepped. It would be quite easy to (safely / easily) cover that with two cheap digital 24hr time switches [1] but a single solution would be 'cleaner'.

Yup and KISS often means at least I actually getroundto doing it. ;-)

Cheers, T i m

[1] Charger timer turns off.

Stepper timer turns off.

Stepper timer turns on. Charger timer turns on.

GOTO [1]

Reply to
T i m

Sounds like a great application for a stepping relay. Typical specs: 10,

20, 25, 40, 50, and up to 100 steps; 2 to 10 poles; 250 V, 2 A.=20

Next; trying to find one.

New ones can be had, but are spendy:

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Reply to
josephkk

0,

SWLedex-1.html

Not really cheap either.

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Reply to
KR

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