L-Adapter - Page 69

alexanderbax · 19th February 2021, 11:51 AM

Quote:

Originally Posted by Salas

Second case is borderline. Dependent on the transformer's regulation percentage and load current asked. You should check if at least 2.5V DC remains across the D11 diode when on the actual application.

Thanks, Salas. Current draw will be around 450ma so not a lot. Will definitely check the DC voltage across the diode on load just to check its stable

Salas · 19th February 2021, 12:02 PM

Alright, let us know.

johnm · 25th February 2021, 05:13 PM

What fuse should one use in the IEC mains inlet socket please? I'm powering a RPi4 which also powers an external SSD. I'm assuming peaks of not more than 3-4A, so would a 4A fast blow be the best bet here? Thanks.

Salas · 25th February 2021, 05:32 PM

You should choose a slow blow primary side fuse based on your transformer's VA rating. That's not to be blowing the fuse by the transformer's inrush current capability at turn on. Primary current is less than secondary current in a step down transformer.

What is your VA? For 230-240V primary and 50VA use around 600mA slow blow. For 100VA around 1.25A.

johnm · 25th February 2021, 08:10 PM

Thanks foe explaining that Salas. Yes it's indeed a 50VA - 600mA fuses ordered

ForsbackaKalle · 19th March 2021, 09:34 AM

Sorry for a silly question. But the LM334 has V+, V- and adjust. 3 pins. How shall it be connected?

Salas · 19th March 2021, 09:42 AM

V+ pin to rail, Rset (12R) between R V- pins, V- pin to LEDS.

ForsbackaKalle · 23rd March 2021, 01:53 PM

Thanks for fast responce. Another question. If I use other leds, like typical round red 3mm leds with about similar 1,9-2 forward voltage. Is it ok?

Salas · 23rd March 2021, 09:37 PM

Should be ok. If they have published specs check their Vf voltage at around 5mA not the usual 20mA nominal value.

Harolda · 27th March 2021, 05:11 PM

I just bought a few boards and mini kits from TeaBag. I am looking at building in total 4 psu's. I will start with a 12V version for a RME ADI2 DAC.
Looking at the transformers I see that most have 2 secondaries. Now i found a 100VA toroid with a single 14.5V secondary and 6.9A. I think this would be perfect for a 12V L-adapter.
I am also looking for a enclosure with heat sinks. Anything else I need to take into consideration?

And would transformers with 2 secondaries be a problem?

regards,

Harold

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19th February 2021, 12:02 PM	#682
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Alright, let us know.

25th February 2021, 05:13 PM	#683
johnm diyAudio Member Join Date: Sep 2003 Location: Hampshire	What fuse should one use in the IEC mains inlet socket please? I'm powering a RPi4 which also powers an external SSD. I'm assuming peaks of not more than 3-4A, so would a 4A fast blow be the best bet here? Thanks.

25th February 2021, 05:32 PM	#684
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	You should choose a slow blow primary side fuse based on your transformer's VA rating. That's not to be blowing the fuse by the transformer's inrush current capability at turn on. Primary current is less than secondary current in a step down transformer. What is your VA? For 230-240V primary and 50VA use around 600mA slow blow. For 100VA around 1.25A.

25th February 2021, 08:10 PM	#685
johnm diyAudio Member Join Date: Sep 2003 Location: Hampshire	Thanks foe explaining that Salas. Yes it's indeed a 50VA - 600mA fuses ordered

19th March 2021, 09:34 AM	#686
ForsbackaKalle diyAudio Member Join Date: Feb 2017 Location: Forsbacka in middle Sweden	Sorry for a silly question. But the LM334 has V+, V- and adjust. 3 pins. How shall it be connected?

19th March 2021, 09:42 AM	#687
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	V+ pin to rail, Rset (12R) between R V- pins, V- pin to LEDS.

23rd March 2021, 01:53 PM	#688
ForsbackaKalle diyAudio Member Join Date: Feb 2017 Location: Forsbacka in middle Sweden	Thanks for fast responce. Another question. If I use other leds, like typical round red 3mm leds with about similar 1,9-2 forward voltage. Is it ok?

23rd March 2021, 09:37 PM	#689
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Should be ok. If they have published specs check their Vf voltage at around 5mA not the usual 20mA nominal value.

27th March 2021, 05:11 PM	#690
Harolda diyAudio Member Join Date: Jul 2005 Location: Oirsbeek	I just bought a few boards and mini kits from TeaBag. I am looking at building in total 4 psu's. I will start with a 12V version for a RME ADI2 DAC. Looking at the transformers I see that most have 2 secondaries. Now i found a 100VA toroid with a single 14.5V secondary and 6.9A. I think this would be perfect for a 12V L-adapter. I am also looking for a enclosure with heat sinks. Anything else I need to take into consideration? And would transformers with 2 secondaries be a problem? regards, Harold