Linear Powersupply built 5 years ago - still going strong - Page 1
Forum section: electronics / general

author: kolbep
author_rank: Frequent Contributor
timestamp: August 26, 2015, 06:53:01 pm
content: Just thought I should share this,About 5 years ago I did an Installation of an Intercom and Access Control for a Complex of 44 Flats.The Intercom, 2 x Sets of RFID Tag Readers, and 2 x Maglocks. All running from a 16v Transformer, Commercial 12v Powersupply, and 12v 14Ah Battery.The Maglocks need power continuously to stay locked.After about 2 months, the commercial powersupply died (Thermal fuse died on it). I think Everything was drawing about 4A continuous.So, Spent a couple of hours designing my own powersupply for it (Still using the same Transformer and Battery).Including Toner Transformer & Etching my board.Worked well, even though the bridge rectifier was a bit warm (small madeup heatsink sorted that out)and the Linear Regulator could not be held comfortably (cant even hold on to its heatsink for too long).Today (after all those years) I went to program in some more RFID tags, and decided that since I still had a key, I should just look if they had replaced it with 1 or 2 of the PowerStore Access Switchmode supplies. I was pleasantly surprised (totally shocked) to see my original powersupply in exactly the same place I left it, still working 100% (although it has a nice layer of dust on it after all those years).I think it is about time they replace the backup battery though (With all the South African loadshedding, I am sure that battery cannot still be holding the doors locked for more than 20 minutes now....)But anyway, I did not expect my creation to last so long..

author: SeanB
author_rank: Super Contributor
timestamp: August 26, 2015, 07:20:04 pm
content: Pieter, funny thing about maglocks is that they will still hold closed to a very low voltage. Found out the gate lock had a dead battery when the battery dropped to 3V with dead cells during the time that the Never Done Correctly was busy replacing neutrals and earths in the substation after they left one morning. Remote receiver would not pull in the relay, but the maglock was happy with 3V and held the gate closed. went and got another used battery, put it in and it worked again.Now, if you are talking about electric fence energisers...........Ah well, tomorrow they come to fix the gate that was damaged by the thieves. now it is mounted again a new maglock is needed. Been busy with helping the razor wire supplier stay profitable. Again. he thinks I am an installer....... Even got some replacement fence insulators to replace broken ones for free.

author: Delta
author_rank: Super Contributor
timestamp: August 26, 2015, 08:47:21 pm
content: Good work, but did you really need a regulated supply for maglocks?

author: McBryce
author_rank: Super Contributor
timestamp: August 26, 2015, 08:52:44 pm
content: Love the heatsink on the rectifier. That's real engineering!McBryce.

author: apis
author_rank: Super Contributor
timestamp: August 26, 2015, 11:18:53 pm
content: Crude but effective.What regulator did you use? I can't quite make out the print under the dust.

author: rolycat
author_rank: Super Contributor
timestamp: August 26, 2015, 11:31:37 pm
content: Quote from: apis on August 26, 2015, 11:18:53 pmLooks like an LM238K.