Question about 555 timer circuit with relays

Ralph · 1st March 2003, 10:32 AM

I found a nice delaying circuit to switch on the B+ circuit of my PSU. It's just what I need:

http://www.ultranalog.com/schem/hvdelay.pdf

I have 4 circuits I want to switch on, all 5V/2A for the 4 rectifier tubes: http://www.homepages.hetnet.nl/~rjonkers/psu.gif

I'm planning to use 4 of these 12V relays http://www.farnell.com/datasheets/7611.pdf that consume 360mW each

* Now my question, can I switch all 4 relays with just a single 555 circuit, or do I need to build 4 circuits like the one above?

* Is it ok to use 13.7v at the input of the circuit (then I will have 12v for the relay as the 555 drops 1.7v)?

Thanks, Ralph

blank527 · 1st March 2003, 10:45 AM

Hi,

For your questions

1 - No I wouldn't do that, because you source the output to much and the 555 will break.
I should put 4 BC560 in parallel and with higher input ressistor (not much)

2- The 555 has a large range of operating voltages, but I would put some stabillity around this IC.. beceause it could affect the output. some elco's close to the IC power should do this job.

Last.. read the datasheet for timing, when the relays comes up.

Grtz,
Remco Blankesteijn

peranders · 1st March 2003, 11:02 AM

I don't agree with Mr. Blank.

First of all: You must get the datasheet of the same brand as the one you have. LM555 isn't exactly the same if we talk ON, National etc. certainly not the CMOS type.

If we take National:

16 volt max as supply voltage and absolute max is 18 V.

Max current is 200 mA, your load is 120 mA.

The only thing you have to think about is to add a diode 1N4001-7 across the relay coils, cathode towards +.

Let me also add, it isn't wrong to be a little bit cautious, a separate transistor doesn't hurt.

Ralph · 1st March 2003, 11:09 AM

The IC will be a PHILIPS SEMICONDUCTORS, Manufacturer Part Number NE555N. Maybe I should look for a relay that consumes a little less power.

Keld · 1st March 2003, 11:19 AM

Quote:

Originally posted by Ralph
SNIP
* Now my question, can I switch all 4 relays with just a single 555 circuit, or do I need to build 4 circuits like the one above?

SNIP
Thanks, Ralph

Or you can let one (smal) relay operate the other 4.

Keld

peranders · 1st March 2003, 11:21 AM

Quote:

Originally posted by Ralph
The IC will be a PHILIPS SEMICONDUCTORS, Manufacturer Part Number NE555N. Maybe I should look for a relay that consumes a little less power.

If Philips also can deliver 200 mA I see no reason why you can use a 120 mA load (4 x 0.36/12).

dhaen · 1st March 2003, 01:39 PM

Ralph,

Why so many relays?
Surely you just need 1 x 2-pole relay per monoblock.
It is only necessary to interrupt 1 heater connection on each rectifier

Cheers,

Ralph · 1st March 2003, 02:42 PM

Hi John

I selected two 2-pole relays from Farnell:

959-455 DPCO, 10A - 44.62 Series
http://www.farnell.com/datasheets/4039.pdf

and

431-382 DPCO, 8A - 40.52 Series
http://www.farnell.com/datasheets/396.pdf

both are rated as 55mA consumption (so 110 together, which is way within the 200mA 555 specs). Will they both be ok?

dhaen · 1st March 2003, 04:53 PM

Ralph,

I think the relays willl be OK. But why 2?

Cheers,

PS Don't forget to add a reverse biased diode across the coil.

Ralph · 1st March 2003, 05:48 PM

Well, the 300B circuit has 2 rectifiers (L+R) and so has the 5687 circuit. That makes 4 high voltage circuits and therefor I need two 2-pole relays.

And I won't forget the diode, it's in the schema I'll build (D1) http://www.ultranalog.com/schem/hvdelay.pdf

1st March 2003, 10:32 AM	#1
Ralph diyAudio Member Join Date: Apr 2002 Location: Culemborg, The Netherlands	Question about 555 timer circuit with relays I found a nice delaying circuit to switch on the B+ circuit of my PSU. It's just what I need: http://www.ultranalog.com/schem/hvdelay.pdf I have 4 circuits I want to switch on, all 5V/2A for the 4 rectifier tubes: http://www.homepages.hetnet.nl/~rjonkers/psu.gif I'm planning to use 4 of these 12V relays http://www.farnell.com/datasheets/7611.pdf that consume 360mW each * Now my question, can I switch all 4 relays with just a single 555 circuit, or do I need to build 4 circuits like the one above? * Is it ok to use 13.7v at the input of the circuit (then I will have 12v for the relay as the 555 drops 1.7v)? Thanks, Ralph

1st March 2003, 11:02 AM	#3
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	I don't agree with Mr. Blank. First of all: You must get the datasheet of the same brand as the one you have. LM555 isn't exactly the same if we talk ON, National etc. certainly not the CMOS type. If we take National: 16 volt max as supply voltage and absolute max is 18 V. Max current is 200 mA, your load is 120 mA. The only thing you have to think about is to add a diode 1N4001-7 across the relay coils, cathode towards +. Let me also add, it isn't wrong to be a little bit cautious, a separate transistor doesn't hurt. __________________ /Per-Anders (my first name) or P-A as my friends call me Tube Buffered Gainclone in work \|Thread

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1st March 2003, 10:45 AM	#2
blank527 diyAudio Member Join Date: Nov 2001 Location: Haarlem	Hi, For your questions 1 - No I wouldn't do that, because you source the output to much and the 555 will break. I should put 4 BC560 in parallel and with higher input ressistor (not much) 2- The 555 has a large range of operating voltages, but I would put some stabillity around this IC.. beceause it could affect the output. some elco's close to the IC power should do this job. Last.. read the datasheet for timing, when the relays comes up. Grtz, Remco Blankesteijn

1st March 2003, 11:09 AM	#4
Ralph diyAudio Member Join Date: Apr 2002 Location: Culemborg, The Netherlands	The IC will be a PHILIPS SEMICONDUCTORS, Manufacturer Part Number NE555N. Maybe I should look for a relay that consumes a little less power.

1st March 2003, 01:39 PM	#7
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	Ralph, Why so many relays? Surely you just need 1 x 2-pole relay per monoblock. It is only necessary to interrupt 1 heater connection on each rectifier Cheers,

1st March 2003, 02:42 PM	#8
Ralph diyAudio Member Join Date: Apr 2002 Location: Culemborg, The Netherlands	Hi John I selected two 2-pole relays from Farnell: 959-455 DPCO, 10A - 44.62 Series http://www.farnell.com/datasheets/4039.pdf and 431-382 DPCO, 8A - 40.52 Series http://www.farnell.com/datasheets/396.pdf both are rated as 55mA consumption (so 110 together, which is way within the 200mA 555 specs). Will they both be ok?

1st March 2003, 04:53 PM	#9
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	Ralph, I think the relays willl be OK. But why 2? Cheers, PS Don't forget to add a reverse biased diode across the coil.

1st March 2003, 05:48 PM	#10
Ralph diyAudio Member Join Date: Apr 2002 Location: Culemborg, The Netherlands	Well, the 300B circuit has 2 rectifiers (L+R) and so has the 5687 circuit. That makes 4 high voltage circuits and therefor I need two 2-pole relays. And I won't forget the diode, it's in the schema I'll build (D1) http://www.ultranalog.com/schem/hvdelay.pdf