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

Construction information for DIY projects, including the MS Mid Side Matrix, Elliptic Equalizer, Mastering Console, Phono Transfer System, Insert Switcher and the Dual Class-A Amplifier. You can post your baby pictures here.
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hlarue
Posts: 2
Joined: Tue Dec 12, 2017 12:38 am

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

Post by hlarue » Fri Nov 20, 2020 4:58 pm

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!

hlarue
Posts: 2
Joined: Tue Dec 12, 2017 12:38 am

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

Post by hlarue » 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
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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.

[...]”

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mediatechnology
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Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
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Re: Powerable from +/-15V supplies using an external 7824 or LM317 regulator

Post by mediatechnology » Fri Nov 20, 2020 6:38 pm

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
https://ka-electronics.com

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