In an earlier thread I was looking for a way to monitor the on/off state of two separate pairs of LEDs using a completely independent circuit which will switch another set of LEDs when a particular two of the monitored ones are on.
My previous efforts have been frustrated by glitches that I'm not experienced enough to figure out -- first of all, all my monitored LEDs suffered a voltage/current overload when the monitoring circuits were connected to them, then today, after I'd replaced the damaged LEDs and added blocking diodes to the interface connections, other LEDs came on when they shouldn't.
So I'm thinking that my best approach is to avoid any electrical connection to the monitored LEDs: Someone in the earlier thread suggested opto-couplers in parallel with the monitored LEDs, to provide a signal for the monitoring circuits, but that would have drawn more current than the LEDs themselves, and potentially overload the 08M2s that are controlling them. What I'm now considering is perhaps using gluing LDRs to the rear of the monitored LEDs, but the size of the sensor ideally needs to be around 2mm diameter so it will fit between the "legs" of the LEDs (standard 2.54mm through-hole mounting).
All I can find with a Google search is several LDRs with a detector size about 5mm x 4mm. Can anyone point me in the direction of a budget-price light detecting device (doesn't have to be a resistor -- anything I can interface with an PICAXE will do) smaller than that, please?
My previous efforts have been frustrated by glitches that I'm not experienced enough to figure out -- first of all, all my monitored LEDs suffered a voltage/current overload when the monitoring circuits were connected to them, then today, after I'd replaced the damaged LEDs and added blocking diodes to the interface connections, other LEDs came on when they shouldn't.
So I'm thinking that my best approach is to avoid any electrical connection to the monitored LEDs: Someone in the earlier thread suggested opto-couplers in parallel with the monitored LEDs, to provide a signal for the monitoring circuits, but that would have drawn more current than the LEDs themselves, and potentially overload the 08M2s that are controlling them. What I'm now considering is perhaps using gluing LDRs to the rear of the monitored LEDs, but the size of the sensor ideally needs to be around 2mm diameter so it will fit between the "legs" of the LEDs (standard 2.54mm through-hole mounting).
All I can find with a Google search is several LDRs with a detector size about 5mm x 4mm. Can anyone point me in the direction of a budget-price light detecting device (doesn't have to be a resistor -- anything I can interface with an PICAXE will do) smaller than that, please?