Electromagnet power consumption

[camelec]

Hi all,

This may seem like a stupid question. However, I have been working on a design that involves an electro-mechanical seven-segment display. Each segment is
is driven by a coil, which from some experimentation can be triggered at 12V and draws around 220mA.

Therefore my question is as these only need to be triggered for 1 msec. Would, four of these devices with all of their coils triggered require a
minimum of a ((7*4)*220) = 6.16A power supply? I've seen other which I would guess would not pull this much current if scaled up. However, I may be totally wrong here.

I have also attached the datasheet for extra information.

Thank you.

[Siwastaja]

If a 1ms pulse is enough to change the state, do not change all the states at the same time. If you have 7*4=28 segments, driving them all sequentially at 1ms intervals would still allow changing all the segments within just 28ms, so the sequence would be just barely noticeable to human eye. If it needs to look instantaneous, maybe drive a few at once, still a significant reduction in peak current compared to driving them all within 1ms. Anything within 10ms looks instantaneous to most people.

This way, peak current is reduced and power supply is much easier to source, also voltage drops, inductive kicks from stray inductance and EMI are all reduced.

[camelec]

Thanks for the quick reply! This definitely seems like the most sensible way.

Cheers.

[Doctorandus_P]

The datasheets specifies a minimum coil voltage of 16V (19V nominal) and a minimum current of 355mA.

So at 12V I would expect the display would not work reliably.
You may have a batch of "good" displays, and your next batch may be "worse".
Maybe the display does not work when it gets hot (sunshine on black, which it needs to be guarded from).
Higher temperature is higher resistance of the copper in the coils, which translates to less current.
Maybe it reduces just lifetime, as the mechanism may get a bit sloppy due to wear.
Maybe some other reason.

It's not smart to ignore the values from the datasheet.