Electrically Isolated Light indicator for a current carrying conductor
Electrically Isolated Light indicator for a current carrying conductor
(OP)
I have a current carrying conductor for a motor pump and require to have an electrically isolated lighting indicator on this conductor. The light indicator should come on when current is flowing in the conductor and off when there is no flow of current. I need a practical simplest of circuits. I was thinking of something like a current transformer connected to a small indicator bulb. I would appreciate your kind contributions. Thanks great guys!





RE: Electrically Isolated Light indicator for a current carrying conductor
Then, it is mostly a question of what intensity you want the lamp to have and what current range the motor works with.
If current changes a lot, a series PTC/R combination can be used to keep light output at reasonable level, it is also possible (actually better) to use an NTC in parallel for the same purpose. Using a LED (or two because of AC) will give you the most lumens for the buck.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Electrically Isolated Light indicator for a current carrying conductor
RE: Electrically Isolated Light indicator for a current carrying conductor
You may need that if current varies a lot. But I think that a 1.5 HP pump motor won't change vary much. Perhaps the starting current can hurt the lamp/LEDs.
Do tis:
1. Find a small non-potted transformer with some space left between core and winding.
2. Put one of the wires through the hole.
3. Connect a couple of LEDs to the primary of the transformer. Connect them in "anti-parallel" so that one LED lights on positive half-cycles and the other on negative ones. A LED usually works over a rather broad current range - from 1 mA to 50 mA should be possible if you run it on half-waves.
4. Short out the LEDs when you start the pump. That will allow a "Life after start".
5. Open the short to see if there is any light at all. If it looks OK, and not too Bright, you should try and stop/start the pump several times to see if the LEDs survive.
If they don't light brightly enough or if they are too bright, you will need to do some measurement and perhaps some calculations. But try it out first - you may be lucky the first time...
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Electrically Isolated Light indicator for a current carrying conductor
Benta.
RE: Electrically Isolated Light indicator for a current carrying conductor
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Electrically Isolated Light indicator for a current carrying conductor
Shorting out the LEDs when starting the pump may not always be a practical idea for my end user . Whatever device I use here should be able to survive at start and after start.However, I am thinking that 3000V rated LED should survive if that is available in the market. Moreover, what voltage and current level would we expect at the terminals of the toroid? Enough to power an LED? My ammeter/voltmeter would not read anything with an improvised toroid of about 20 turns.
RE: Electrically Isolated Light indicator for a current carrying conductor
The shorting out was precautionary the first time you start. Just to make sure that the LED doesn't burn out directly. If the LED lights "normally" - whatever that is, you can skip the shorting out.
Twenty turns and one primary turn would produce 5A/20, which is much too much and at too low a voltage. Try 500 turns instead, that should give you around 10 mA.
But DO NOT use a ferrite toroid - you need transformer plate here. So, a non-potted transformer might serve you better after all. The winding is already there.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Electrically Isolated Light indicator for a current carrying conductor
http://www.johnsoncontrols.com/content/dam/WWW/jci...
There are other similar devices on the market.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Electrically Isolated Light indicator for a current carrying conductor
RE: Electrically Isolated Light indicator for a current carrying conductor
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Electrically Isolated Light indicator for a current carrying conductor
http://www.nktechnologies.com/current-sensing-swit...
They have an LED indicator built-in, but they also have a relay output that changes state when current flows and you can use your existing 120V to power a pilot light.
"Will work for (the memory of) salami"
RE: Electrically Isolated Light indicator for a current carrying conductor
"Will work for (the memory of) salami"
RE: Electrically Isolated Light indicator for a current carrying conductor
Thanks great guy!
RE: Electrically Isolated Light indicator for a current carrying conductor
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Electrically Isolated Light indicator for a current carrying conductor
Digikey
CR Corp (very cool)
The one I use most
Keith Cress
kcress - http://www.flaminsystems.com
RE: Electrically Isolated Light indicator for a current carrying conductor
http://www.crmagnetics.com/Products/CR2550-P13.asp...
Can't beat the price at $12.35, either.
SceneryDriver
RE: Electrically Isolated Light indicator for a current carrying conductor
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Electrically Isolated Light indicator for a current carrying conductor
RE: Electrically Isolated Light indicator for a current carrying conductor
Always helps when you know exactly what you're looking for. :)
Keith Cress
kcress - http://www.flaminsystems.com