Author Topic: Can you help me calculate this for 24V instead of 12V?  (Read 946 times)

KarenColumbo

Re: Can you help me calculate this for 24V instead of 12V?
« Reply #20 on: December 13, 2020, 04:53:40 PM »
Beautiful, thank you. Logic isn‘t my thing ... well, this concludes that :)
@ Zener: I got this from Rod Elliott‘s article about relays. ( https://sound-au.com/articles/relays.htm It speeds up the deactivation of the coil and thus avoiding undue ageing.
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Rob Strand

Re: Can you help me calculate this for 24V instead of 12V?
« Reply #21 on: December 13, 2020, 05:24:45 PM »
Quote
Beautiful, thank you. Logic isn‘t my thing ... well, this concludes that :)
@ Zener: I got this from Rod Elliott‘s article about relays. ( https://sound-au.com/articles/relays.htm It speeds up the deactivation of the coil and thus avoiding undue ageing.

The stuff Rod Elliot mentions about the turn off times is all true.      Basically you have a trade-off:   The higher the voltage you allow across the coil the quicker it turns off.   However the more voltage you alllow across the coil the more stress on the switching transistor.    The higher voltage can be achieve with a series resistance or a zener.   With the series resistor method the voltage starts high and then immediately start to drop. The zener keeps the voltage high for longer so the coil discharges quicker for a given maximum voltage.

IMHO, if the contacts aren't pulling any current (like audio signals) there would be very little reduction in ageing with faster turn-off times.   There's no arcing causing contact stress.     When the coil is turned off the contact force slowly drops as the coil current reduces until the spring wins.    If you are switching high currents the point were the force is lowered can promote arcing and high resistance joints at the contact and that would reduce the life of the contact.

So for audio signals speeding-up relay switch off is solving a problem that doesn't need to be solved - well not unless you *need* fast contact turn off.   There's probably a turn-off time that sounds less glitchy.
« Last Edit: December 13, 2020, 05:26:33 PM by Rob Strand »
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iainpunk

Re: Can you help me calculate this for 24V instead of 12V?
« Reply #22 on: December 13, 2020, 06:07:58 PM »
Wow, thank you, Antonis, that really gets me started!!

Do you have some patience left for me? N0000b time!!  :icon_redface: :icon_redface: :icon_redface: :icon_redface: :icon_redface:

If so: Why won't this work? I mean, obviously I can toggle those LEDs, but the relay won't act. I think I'm shorting something out with the PNP snippet in there.

What I intended: If the switch is closed, LED 1 lights up. If the switch is open, LED 2 should light up. [[▲The 3906 is really a BC559, forgot to change that in Eagle, sorry]]




have you considered this current path?

it can be resolved by changing the switch contacts around. the middle lug goes to the transistors, the outer lugs go to ground and 12V,

cheers, Iain
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