Connecting a relay

DragonMaster · 27th February 2005, 02:01 PM

I installed a relay in a bionaire humidifier to prevent the water sponges from drying.(The fan stops at the same time the empty light starts)

I'd ask a couple of questions:
1. How can I prevent the spark from happening when the motor is re-starting(When I fill it)
2. Is it OK if the relay coil feels hot thru the humidifier's plastic case?

richie00boy · 27th February 2005, 02:46 PM

To reduce relay contact arcing, add a capacitor (100nF or so, high voltage) across the contacts.

The relay coil should not be hot! Have you chosen the correct coil voltage? There are different voltage ones as well as AC and DC ones.

DragonMaster · 27th February 2005, 04:28 PM

Where do I put this cap, between hot and motor?

Quote:

The relay coil should not be hot! Have you chosen the correct coil voltage? There are different voltage ones as well as AC and DC ones.

It's powered on 120VAC and is a 125VAC coil. Well, maybe it's just warm.

Also, when the coil is active, there's interference in the TV picture.(And when the coil changes position, even when the contacts are unplugged, we see it in the picture and hear a pop)

EDIT:
I found it's supposed to be warm here:
http://www.naisweb.com/e/relaye/mech...i/idamo5w.html

It's an AC coil.

Frank Berry · 27th February 2005, 05:02 PM

Add the capacitor across the HOT contact and the contact the feeds the humidistat and motor. You might reduce the arcing even more if you add a little resistance in series with the capacitor.

DragonMaster · 1st March 2005, 01:06 PM

100nF, even with AC?

richie00boy · 1st March 2005, 01:50 PM

I use a 4700nF Y rated capacitor as if that fails it will fail open.

DragonMaster · 2nd March 2005, 10:35 PM

And what do I do for the coil interference?(In the TV)

richie00boy · 3rd March 2005, 06:44 PM

I can't see how energising a relay coil causes major EMI. Have you definitely checked there is not something else wrong? You could try connecting another of those Y rated caps across the coil to snub noise as a last resort. I think the problem lies elsewhere though.

DragonMaster · 3rd March 2005, 09:38 PM

Low band VHF signals are affected(2-6).

When I listen to one of these on my PC monitor , there are bright vertical noise stripes in the picture.

The coil is AC(Maybe there's a difference) and 1/3HP.

27th February 2005, 02:46 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	To reduce relay contact arcing, add a capacitor (100nF or so, high voltage) across the contacts. The relay coil should not be hot! Have you chosen the correct coil voltage? There are different voltage ones as well as AC and DC ones. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

27th February 2005, 05:02 PM	#4
Frank Berry diyAudio Member Join Date: Sep 2003 Location: Midland, Michigan	Add the capacitor across the HOT contact and the contact the feeds the humidistat and motor. You might reduce the arcing even more if you add a little resistance in series with the capacitor. __________________ Frank

1st March 2005, 01:06 PM	#5
DragonMaster diyAudio Member Join Date: Dec 2003 Location: Montreal	100nF, even with AC? __________________ Antoine http://dmsaudio.ca/

1st March 2005, 01:50 PM	#6
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	I use a 4700nF Y rated capacitor as if that fails it will fail open. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

2nd March 2005, 10:35 PM	#7
DragonMaster diyAudio Member Join Date: Dec 2003 Location: Montreal	And what do I do for the coil interference?(In the TV) __________________ Antoine http://dmsaudio.ca/


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3rd March 2005, 06:44 PM	#8
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	I can't see how energising a relay coil causes major EMI. Have you definitely checked there is not something else wrong? You could try connecting another of those Y rated caps across the coil to snub noise as a last resort. I think the problem lies elsewhere though. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

3rd March 2005, 09:38 PM	#9
DragonMaster diyAudio Member Join Date: Dec 2003 Location: Montreal	Low band VHF signals are affected(2-6). When I listen to one of these on my PC monitor , there are bright vertical noise stripes in the picture. The coil is AC(Maybe there's a difference) and 1/3HP. __________________ Antoine http://dmsaudio.ca/

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