Elektor amp inrush current limiter question - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 22nd September 2002, 11:07 PM   #1
diyAudio Member
 
Join Date: Mar 2002
Location: Torrance, CA
Default Elektor amp inrush current limiter question

In this thread there's a neat little diagram of a current inrush limit very similar to what I was thinking of building.

It references a link to http://mitglied.lycos.de/Promitheus/...or_toroids.htm which is apparently an Elektor magazine circuit.

My question is what is the C1 bypass cap in the circuit diagram for? They spec 330n, but from Mouser I'm having problems finding that, so was thinking of using either .22uf or .47uf X2 caps (if my ancient EE degree hasn't confused nano, pico, and micro).

Actually, when I look at the whole front part of the curcuit it looks a little weird - the RC time constant seems to be R1,2,3 + C2,3, with the rectifier bridge in the middle? Hmm .. I guess that would work OK, but I don't see a voltage divider so I assume you've got to match the relay resistance with R1,2 and 3 to get the right voltage on the cap's.

Thank you,
__________________
== John ==
  Reply With Quote
Old 23rd September 2002, 01:54 AM   #2
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
I tried this circuit. My realay was 12V, 120ohm and I couldn't get it work with sufficient delay time. All I got was less than 2 sec. and the 2 resistors (470 kohm) had to be replaced by 1k ohm to get 8V voltage drop on relay. I don't know what 330nF cap is doing there, but it seems like the circuit is suited for high resistance relays only.
__________________
www.audiosector.com
Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it. - JC
  Reply With Quote
Old 23rd September 2002, 03:09 AM   #3
diyAudio Member
 
Join Date: Mar 2002
Location: Torrance, CA
Interesting - given it's Elektor, I imagine it could be sized for 240v mains? I couldn't find the relay spec on the web page I posted.
__________________
== John ==
  Reply With Quote
Old 23rd September 2002, 05:02 AM   #4
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
It may be true that this circuit works better with 240 mains. The only info on relay is: 24V (250V-8A contact).

I couldn't get this circuit working with my relay.
__________________
www.audiosector.com
Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it. - JC
  Reply With Quote
Old 23rd September 2002, 06:22 AM   #5
diyAudio Member
 
Join Date: Mar 2002
Location: Torrance, CA
Well, I could run this off a 12v coil in the xformer I was looking at; if I do this, then I'd probably have to switch in the resistors on the rail side of the transformer. It would give me a headache to figure out how much resistance on the main side would affect a capacitor on the low side

That was my original idea anyway; too bad, it would have been nice to order these PCB's.
__________________
== John ==
  Reply With Quote
Old 23rd September 2002, 08:26 AM   #6
hifi is offline hifi  Sweden
diyAudio Member
 
Join Date: Mar 2001
Location: sweden
i think the original article spec a 1100R relay for the right voltage drop Elfa (in Sweden) has a very fitting relay with driving 16-42,2V range. but i would still want to put a zener across that relay just to be sure..

if you use a 12V relay the two 470F would need to be increased like ~4 times to get the same rise time.



/micke
  Reply With Quote
Old 23rd September 2002, 10:44 AM   #7
diyAudio Member
 
wuffwaff's Avatar
 
Join Date: Aug 2001
Location: Ingolstadt Germany
I use this circuit for my Aleph5 (2 x 600VA toroids). It is for 230V operation and works all right with the specified values (relais 24volt/1200 ohms).

For my crescendo I use a circuit thats based upon a 555 timer ic, so you can set the delay as you like but you need a seperate 12V supply.

william
__________________
een ooievaar is geen konijn want zijn oren zijn te klein!
  Reply With Quote
Old 23rd September 2002, 11:22 AM   #8
yeti is offline yeti  Germany
diyAudio Member
 
Join Date: Nov 2001
Location: Ewersbach
Default C1

This cap is used as a Resistor (Rc1 =1/2*pi*f*C1) the two 470 K resistors are used to discharge it.
The current for the relay will flow through the capacitor, wich will not get warm as a resistor would do.
So you can calculate C1 by the current requirement of your relay.

regards Arne
  Reply With Quote
Old 24th November 2003, 09:41 PM   #9
diyAudio Member
 
Join Date: Nov 2003
Location: In Aalborg
will the 330n capacitor not be discharged through the 220 resistor? I have a 24V DC relay with a rated coil current of 21,8mA. I assume this current is constant both when the contakt is on and off. Is it correct? With a 330n capacitor, the voltage drop across it will be approximately 230V, not leaving much voltage to the rectifier circuit. Even though it is written that the charge time constant only depends on the the two 470 micro caps, the 220 resistor will also influence? Tau=R*C
  Reply With Quote
Old 2nd December 2003, 09:23 PM   #10
Kram is offline Kram  United Kingdom
diyAudio Member
 
Join Date: Jun 2002
Location: Durham UK
Default Another question about this circuit.

Hello,

I am thinking of using this circuit and was wondering if using 4 1N4004 diodes would be ok (safe) to construct the bridge rectifier from? If its important I live in the UK, 240V mains here in case you didnt know.

Thank you.
Mark.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
inrush current limiter! lanchile Chip Amps 7 2nd February 2009 10:20 PM
Question on Inrush Current Limiter pwan Pass Labs 4 16th April 2006 04:06 AM
Inrush current limiter? roger-k Pass Labs 4 19th February 2006 08:42 PM
CL-60 Inrush Current Limiter ljozsef Pass Labs 8 11th February 2004 10:40 PM


New To Site? Need Help?

All times are GMT. The time now is 09:26 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2