Hi all,
Since this cartridge circuit is 1,2v / 0.5mA - is there anyway I can wire in a Red LED indicator into the circuit to indicate the cartridge is ‘On’?, as from what I’ve read Red LEDs require circa 1.7v + to get them to light up!
This is for the left switch. The right switch should be easier as it will control the power from the Charger to the Batteries and will be at a voltage which can be ‘reduced’ to light and LED.
Thanks,
nige
Sorry if its a dumb question for some…
The switch is before the big dropper resistors?
If so, the voltage at the switch is above 2V, so you run a small dropper resistor from the switch to the LED, check out the LED datasheet for suggested current and work out the voltage drop to derive the LED resistor value.
Thanks, I’ll get the voltmeter out and check it.
Yes the switch is before the resistors - the positive output feeds the resistors and the negative is fed from the ‘negative’ terminal on the back panel. Not sure if that makes a difference?
So I’m using both poles of the switch, probably ‘overkill’ but felt better to do it that way.
Thanks,
Hi, yes checked this out this morning, the advantages of a home office day, so all good - i do really appreciate the people that know what they’re doing…
So just need to go back to the resistance / voltage calculator to determine suitable resistor value.
Thanks,
N
Personally, I’d put a small, incandescent bulb somewhere in the circuit rather than an LED 
Hi, can you explain why?
What the advantages of a small incandescent bulb over and LED?
Thanks
I really don’t know if the effect of a diode working in this proximity would be audible but if I had to put a lamp in at all it’d probably be something not switching. It’s easy enough to try the diode in circuit and see whether it is audible, if not all’s good. If it is audible (in that situation) then try a filament bulb. Maybe use it to drop a little voltage instead of some of the resistance.