Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Captain chunkulus on June 21, 2019, 07:52:06 am

Title: 28v ct tap for 5v relays.
Post by: Captain chunkulus on June 21, 2019, 07:52:06 am

Have a transformer that has an extra 28v ct tap. Would like to use it for 5v relays. Can I just use anow lm7805 to drop it down or do I need to do something more drastic? Thanks.

Title: Re: 28v ct tap for 5v relays.
Post by: shooter on June 21, 2019, 08:37:01 am

IIRC the lm7805 is good to 35vdc IN, double check though

Title: Re: 28v ct tap for 5v relays.
Post by: DummyLoad on June 21, 2019, 08:58:22 am

use 14V (CT to end) and LM7805 or use the part in the link below.


http://www.ti.com/product/TL783


--pete

Title: Re: 28v ct tap for 5v relays.
Post by: sluckey on June 21, 2019, 09:12:05 am

If you use that 28V w/CT (14-0-14) with a two diode conventional rectifier and a 470µF (or larger) cap you will get about 20VDC. That's fine for a 7805.

Title: Re: 28v ct tap for 5v relays.
Post by: PRR on June 21, 2019, 12:03:38 pm

12V relays would be a better fit, but don't run out to buy some.

Title: Re: 28v ct tap for 5v relays.
Post by: kagliostro on June 21, 2019, 12:10:13 pm

There are also 24v relays

https://www.ebay.it/itm/Omron-G5V-2-24V-DC-PCB-Mount-Signal-Relay-DPDT-OM0349a-/390274026615 (https://www.ebay.it/itm/Omron-G5V-2-24V-DC-PCB-Mount-Signal-Relay-DPDT-OM0349a-/390274026615)

(https://i.ebayimg.com/images/g/aRkAAOSwyOVcwx8c/s-l1600.jpg)

Franco

Title: Re: 28v ct tap for 5v relays.
Post by: Captain chunkulus on July 01, 2019, 08:40:26 am

Thanks guys for all your help.  :worthy1: