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Old 04-07-2007, 09:15 PM   #1
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Default Digital 120v timer voltage bleed

I have installed a digital timer that is supposed to make and break a circuit according to sunrise and sunset. The display interface is LCD and the unit seems to be electronic internally. I need this timer to operate a relay with a 120v coil. The timer when in the off setting bleeds votage. It seems this may be intentional to provide power to the timer itself to operate off of, otherwise known as a power stealing device. It bleeds about 66v when off which is not enough to properly energise the relay but it is enough to cause the relay to make a horrible chatter and I'm sure it is not good for the relay coil. Could a resistor across the hot and neutral wires to the relay coil eliminate this problem? If so what size resistor should I use? Any other suggestions that could make this work? Thanks in advance.
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Old 04-07-2007, 09:34 PM   #2
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RIX start with an incandescent lamp across the terminals if this resolves the issue, the try a variety of resistors. I say this because I do not know what size might work.
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Old 04-07-2007, 09:39 PM   #3
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good idea Brian, thanks...
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Old 04-07-2007, 09:52 PM   #4
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Flashback....

I seem to remember this issue with the AllenBradley PLC 1. (okay, you can quit laughing now)

The outputs would leak such that many relays would chatter. At that time, AllenBradley made a thing you wired in series with the hot wire to the relay coil. Don't quote me on this, but I'm pretty sure it was a 220 ohm resistor in series with a .39 microfarad cap, but it was in one square package and officially called a "contactor surge suppressor". (sometimes, numbers stick in my head. this was mid 80's, so I might be foggy) Solved the relay chatter issue, in any event.
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Old 04-07-2007, 10:30 PM   #5
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I'm by no means an electrical engineer, but it seems to me the trick is to provide a bleed loop that has less resistance than the coil circuit but not so little as to create a short and at the same time not effect the relay's ability to close when full 120v is present.
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Old 04-07-2007, 10:36 PM   #6
 
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what is the type and model of time clock, some of them you can seperate the timer circuit/
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Old 04-07-2007, 10:57 PM   #7
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I do not believe the timer circuit can be seperated with this particular unit. It does have battery back up for clock and programming. It is a residential unit made by Intermatic. Mod # EJ500C. Instruction manual and fact sheet are at the bottom of the page linked below.
http://www.intermatic.com/Default.as...cid=43&sid=112
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Old 04-08-2007, 05:44 AM   #8
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Possible put consecutively with relay coil pair of diode-thyristors. However even cheap chinese digital timers (10$) do not deliver such problems. A pair of the months back I happened to collect control system by illumination of the perimeter and light advertisment. I was shown that in such events practical to use simply luminosity sensors (2-5$), without timer. Originally, the system concluded in itself both timer, and sensors (not to count other components). But hereinafter became obviously realized that without timer handy and reliable. Understandable that this not for all events.
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Old 04-08-2007, 06:14 AM   #9
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Occam's Razor

"The simplest explanation for some phenomenon is more likely to be accurate than more complicated explanations."

. . .or in the only form that takes its own advice. . .
"Keep things simple!"


The timer is defective, take it back and try another.
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Old 04-08-2007, 08:32 PM   #10
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Quote:
The simplest explanation for some phenomenon is more likely to be accurate than more complicated explanations


John: In making my post I violated one of my basic rules, check the simple thinks first. Checking with the manufacture is a simple enough and they would be able to tell you if this in normal or abnormal.

It is possible this unit is defective, or that it is not designed to operate relays..

Keep us on our toes.
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Old 04-09-2007, 01:12 AM   #11
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Whether you broke one of your rules or not Brian, still a good idea for a starting point. The timer is not broken. It just will not work in my application without modifying. I do not know how to make the modification or if it would be cost effective to do even if someone were able to tell me how; hence my post to this forum. Through research at the manufacturer site it appears this timer is designed with intent to operate incandescent bulbs exclusively. I found an alternative timer they offer which costs double of course. Model SS8 has the same self adjusting sun up/sun down function and footprint of the solid state model I have been trying to get to work that instead uses a small internal motor that is energised by the timer to actuate the load switch. I presume the voltage leak is needed by the solid state timer in the EJ500C model in order for it to operate. I would still be curious though if there is a fix for this.
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Old 04-09-2007, 08:07 AM   #12
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Quote:
Originally Posted by brian john View Post
Keep us on our toes.
I do not want the responsibility of keeping everybody on their toes, I have enough trouble just watching over myself.

Quote:
Originally Posted by RlxdN10sity View Post
I would still be curious though if there is a fix for this.
Try this part it is a Allen Bradley coil suppressor(599-K04) used to limit voltage transients for applications requiuring interface with soild state components.

Attachment 109

Last edited by John; 04-20-2007 at 12:48 PM.
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Old 04-09-2007, 08:21 AM   #13
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Well possible put light bulb on leaving the timer, in parallel of relay coil. If put resistor instead of lamp, power will as lamps, but all power go in heat. However possible use contact group of relay for unhooking this resistor for prevent surplus heating.
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Old 04-09-2007, 09:52 AM   #14
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Quote:
Originally Posted by John View Post
Try this part it is a Allen Bradley coil suppressor(599-K04) used to limit voltage transients for applications requiuring interface with soild state components.

Attachment 109
On second thought this will not work.

The work-around would be just to buy the other timer. You will just smoke your brain trying to find work-around.
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Old 04-09-2007, 10:55 AM   #15
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Yeah, I had actually already bought and installed the other timer just prior to making my last post. I posted this issue to 3 other forums and you guys were the most capable of coming up with ideas. I thought it could have been something some of you have dealt with before and there may be a known fix. I really appreciate all of your time and effort. Thanks.
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