Electronics > Projects, Designs, and Technical Stuff
How to use the same RELAY on 12V & 24V vehicles
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JDW:

--- Quote from: soldar on August 09, 2019, 06:53:10 am ---Dual voltage relays: https://www.newark.com/space-age-electronics/ssu-pam-2/relays-control-spdt-24v-7a-panel/dp/08N1908

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Too large and much too expensive even in high volume.  Again, I am considering Hongfa relays for size and price reasons.  I've used them in the past so I know the quality is good.  In other words, the relay cost is restricted to less than US$2.
MosherIV:
In automotive electronics, the circuit has to be able to withstand voltage surges and drops BUT not necessarily work at the extremes. It depends what the circuit is being used for (sorry I forgot what the original post said).
My thoughts if it helps.
soldar:
In case it is of use for others reading:

--- Quote ---The SSU-PAM-4 Relay provides 10.0 Amp Form C contacts.
The relay may be energized across a wide voltage range from 9VDC to 40VDC.
The 15mA operating current is constant across the operating range.
The input DC voltages are polarity sensitive and diode protected.

The SSU-PAM-2 Relay provides 7.0 Amp Form C contacts.
The relay may be energized by one of two (2) input voltages: 12VDC or 24VDC.
The input voltages are polarity sensitive and diode protected.
A red LED is provided which, when illuminated, indicates the relay coil is energized.
https://www.newark.com/space-age-electronics/ssu-pam-2/relays-control-spdt-24v-7a-panel/dp/08N1908
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Probably integrates the electronic current control.
soldar:

--- Quote from: soldar on August 08, 2019, 03:51:46 pm ---
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By the way and just in case anybody is interested, this was the circuit normally used to maintain constant motor speed in battery powered cassette players. If the battery set was nominally 6V, the player would use a 3 or 4 volt motor and use a similar circuit to limit current and motor speed would remain constant as the battery's voltage declined.
floobydust:
OT I don't think so, constant current does not give constant speed. Low cost cassette player motors have centrifugal switches for constant speed or a tachogenerator.

That circuit you post is a disaster - from 24-12V with a 0.5A coil?! 12W of heat total? It's a coffee warmer.
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