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Powerable from +/-15V supplies using an external 7824 or LM317 regulator

Posted: Fri Nov 20, 2020 4:58 pm
by hlarue
Recommendations welcome.

Not finding a solution that takes both the + and - 15V DC from the Meanwell PS and converts to the +24V DC necessary for the Insert boards.

Thanks in advance!

Re: Powerable from +/-15V supplies using an external 7824 or LM317 regulator

Posted: Fri Nov 20, 2020 5:19 pm
by hlarue
Found this, which was super helpful; looking for an example of the implementation, if possible:

“Re: Mid Side M-S Matrix Construction Information
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Post Mon May 16, 2016 3:49 am

[...]

The bypass board is 24V (using 12V relays).
The coil connections float and are not tied to any ground.
Thus, if you only have +/-15 to +/-18V available you can sub-regulate the available 30 to 36V down to 24V using a 7824 or LM317 regulator.
In this configuration the regulator IC and relays common to the -15V (or -18V) rail.
The +15V rail (+18V) connects to the regulator input.
The regulator output provides +24V relative to the minus supply rail.
The relay coils "see" 24V and the relay current returns to the negative supply rail instead of 0V.

[...]”

Re: Powerable from +/-15V supplies using an external 7824 or LM317 regulator

Posted: Fri Nov 20, 2020 6:38 pm
by mediatechnology
hlarue wrote:
Fri Nov 20, 2020 5:19 pm
Found this, which was super helpful; looking for an example of the implementation, if possible:

“Re: Mid Side M-S Matrix Construction Information
Report Quote
Post Mon May 16, 2016 3:49 am

[...]

The bypass board is 24V (using 12V relays).
The coil connections float and are not tied to any ground.
Thus, if you only have +/-15 to +/-18V available you can sub-regulate the available 30 to 36V down to 24V using a 7824 or LM317 regulator.
In this configuration the regulator IC and relays common to the -15V (or -18V) rail.
The +15V rail (+18V) connects to the regulator input.
The regulator output provides +24V relative to the minus supply rail.
The relay coils "see" 24V and the relay current returns to the negative supply rail instead of 0V.

[...]”
Good find. Exactly what you need to do.

You need a 7824 regulator with heatsink.
The regulator board's ground should not have a connection to chassis.
eBay would be a good place to look.
Connect the Meanwell's +15V output to the 24V regulator Vin.
Connect the Meanwell -15V output to the 24V regulator Gnd.

The 24V "Gnd" connection is really at -15V and will be the switch common and will also connect to the insert board Relay Gnd pad.
The regulator board +24V output will connect to the Insert Switcher +24V connection.

The -15V line