Electronic Circuits and Projects Forum

I happen to stumble upon this thread because of the title.

I remember the old thread. I put a circuit together as I recall using a 4017 to drive the ULN2003 chip. That is strange as pins 11 & 10 would be the pins 6 & 7 inputs. See the attached as I found some remnants of the circuit I suggested. Just peculiar the first inputs / outputs work and the last two don't work. If you have a meter depending on how you are clocking the 4017 you could see if the input pins are going high when they should?

Ron

Hi Peter

If we look at the data sheet for the PC814 series we notice it has two LED emitters placed back to back. The incorporating of two LED emitters rather than a single makes it useful for AC signals. If we apply an alternating current to a single LED emitter opto coupler we get pulses out on the alternate half cycles of the AC input when the LED is forward biased. Using two emitter LEDs back to back in a single package we get a constant output for the AC input since each LED will conduct on alternate half cicles. One or the other is always on.

Ron

Glad that worked out.

Generally in the wonderful world of opto couplers we like to think of them as used in DC applications. However, there are applications where an AC signal may be present and we need to use it. For example a ring signal on a phone line. The ring signal is an AC sine wave riding on a DC level. I could block the DC component using a capacitor to pass only the AC ring signal and divide that AC down and pass it along to the opto coupler designed for AC. I could then detect the AC ring signals on a phone line. Sort of abstract example but it came to mind. There are plenty of other uses, I believe the data sheet mentions common applications.

Ron

Hard to call or say how they are using them without a schematic. With things like this the best shot is looking at the board and trying to map things out. From the data sheet we know the input and output of the opto so it is a matter of what feeds it and what the out is connected to. What exactly does the board do? Also, many of today's hot tubs get pretty elaborate with switching pumps etc as well as temp control.

Ron

Hi Peter

Sans a drawing these things are almost impossible to figure out. You can look at known parts and guess how a board works but that is about as good as it gets depending on one's skill level. Like you mentioned seeing the triacs for the blower motor. Funny a hot tub came up as I see one in the near future with a new deck in the yard.

Ron