My soldering skills have been on the decline and instead of moving my DIY controller from the breadboard again to the circuit board I decided to get a Milwaukee pH controller. I don't want to mess with the circuit board again. Since the Milwaukee isa lovely yellow-green and the solenoid light blinks when it's on, I decided to move it inside the cabinet. I like being able to see the solenoid on at a glance, however, and decided to add an indicator light. The circuit is very simple and consists of:

a small plastic box (an old asprin bottle would do) to house the components.
one foot of speaker wire
0.47 uF non-polarized capacitor, >200V
56K ohm 1/4 watt resistor
IN1004 diode
Red LED
Plastic diode mount pressed in a hole drilled in the cabinet.

The diode is needed because I'm lighting the LED with AC current from the plug on the solenoid; one end connected to the capacitor and the other to the resistor The capacitor and resistor drops the voltage to about 10 volts and the circuit runs cool with sufficient brightness from the diode.

Schematically, the LED and the diode are joined in parallel, anodes to cathodes. At the LED anode junction one end of the capacitor is attached. The resistor is attached at the LED cathode junction. The free ends are connected in parallel with the solenoid. In practice, the speaker wire is used to connect the LED to the diode and the capacitor and resistor leads to the solenoid.

Ooookay... would you mind doing a little MS Paint thingy to show how you soldered it all together? Are you running the LED on 10V? Seems kinda high to me, maybe depends on the LED.

I've got some of those highly prized Stealth heaters, they are so stealthy that they even hid the indicator light, but it would be good to know sometimes if it is on or off... a little LED solution would be excellent. Do you know of any way to set up a similar circuit that lights a LED if there is a certain current being drawn, and turns it off if the heater is off?

I'll cobble something together soon. I was going to do it the old fashion way but html doesn't hold place like text files.

The 10V is across the capacitor and LED. The LED voltage drop is about 1.7V.

I'll revise the drawing eventually to show the voltages.

Wiring the heater would require surgery and I don't know if you could seal it water-tight. Very, very important. It like the radios that falls in the tub. That's B. A. D. All you would need is a wire in parallel with the heating coil so the light comes on when the heater is on. Be careful. Be very careful.

Thanks, that clears it up.

I am not suicidal... yet and wasn't going to cut the heater open. I was thinking of a little plug-in module thingy, with a trigger that senses when some amps flow vs when not. Different from your circuit, maybe more difficult, maybe there is no such thing.

I'm thinking about this and maybe there's a solution. Good grief, the heater draws e.g. 150 watts so there may be a way to attach a wire or coil to pick up the inductive load from the heater. All you may need is a op amp or transistor to serve as a switch. Let me see what I can find. Of course, if anyone knowledgable with electronic knows how to do this, your input would be greatly appreciated.

You could just run the power cord thru a small coil, and use the coil voltage to switch a light on. It would act as a transformer, much as clamp on ampmeters work. I don't know for sure, but I suspect you could buy such a contraption.

Buy it? And miss all of the time, expense, frustration and aggravation of making something that may or may not work Forget it!

Oops! Sorry. I forgot the real reason we all do DIY projects.

That reminds me: years ago when the cassette recorder first became available I got one and built an adaptation to allow me to mount it in my car (one of the original Torota Coronas imported to the USA), so it would play thru the car radio. (It was a 120vac powered recorder, of course.) I was proud of myself and figured I would always have a one of a kind installation. Like most of my DIY projects it was really clunky, but it worked. OK, back to your regularly scheduled program.