- 27 Oct 2009
You remember the time-honoured saying that a little knowledge is dangerousUsing a resistor to drop voltage is a time-honored method for a device with constant current.
dropping 6 volts through the resistor directly states that you have .088 amps through the circuit, i.e. unless the optocoupler is a CONSTANT 88 milliampere load, then you are NOT regulating the voltage to 1.5 volts (and for that matter are you sure your 7.5 voltage is also CONSTANT?
So, you are desiring the optocoupler to be an isolated switch.
so, the absolute max rating on the "transmitting" diode in the 3021 is 60 milliamperes. If your voltage reading is correct, you should have already blown this diode up. It's and LED, so you need to calculate the CURRENT in the transmitting diode, not the voltage, just like an LED headlight.
Once past that, your next hurdle is that the receiving side inside is indeed a triac, which will not turn on and off with DC, used for AC only.
So, if you want to use an optoisolator, you need a different component.
However, I am tying - very trying
At least I saved you from having to shoot yourself - although the frustration to my very simple mind is that I can't find a solid state device that will work like a relay - I thought I had that with the optocoupler that I bought. The problem with many components is that all of the information is not necessarily found in one place.
With Google as my friend, having found the optocoupler that appeared, in diagramatic form, to do what I needed, I then in another place found that the feed voltage was fairly low at 1.5v (that figures as there's an LED in it) but it was only when I was searching further after my failed attempt that I found mention of it being a triac and therefore for AC - so three places to find that much info and the third bit too late.
Looking back at Tony Walsham's post about the Mylocosound card - as far as I can make out, while it doesn't need an Annie or Connie type chuff trigger, it's sound pulses don't hook up to the Bachmann optosensors, it relies on voltage draw (unless it's been upgraded and there's more info that's not on Google).
Neil, I think I'll need to disconnect the optocoupler to check that. I've been wandering about thinking what to do, and what is now obvious is to take the optocoupler circuit out.If you back to the configuration in post number 10 where you state you got it to work with a 9V supply in the tender, does shorting the chuff wires to each other still produce a chuff as before?
I'll do that and report back - before I shoot myself