mm....scratch did not work....

Hi,
measure the voltage across R1 with the buffer amp output high, do the calculation to find the current thru R1.
Most optoisolators have approx. unit current gain across the opto boundary. Thus if you have 1mA input thru the photodiode then the
phototransitor will have  approx. 1mA in emitter/collector circuit. Most PCB relays will need 20mA for reliable operation,
ie you should aim for 20mA in the photodiode.

Another possibility to increase the sensitivity of the phototransistor is to bias the base. It is for this reason that the base is
pinned out. Use a resistive voltage divider to apply 0.55-0.58V or so to the base. If you bias to high or circuit conditions change,
temperature for instance, you risk having the phototransistor conduct WITHOUT the photodiode conducting!

Craig

A quick question:
Is this schematic correct?
https://karusisemus.files.wordpress.com/2016/07/sch.png

Hi
correct in what sense...it will not work for a relay. The 4.7k resistor permanently powers a relay coil if hooked to
an output and the phototransistor shorts the coil...all for what?

Craig

Hi,
just been dealing with a spotwelder/dent puller at work based on triac control of a transformer of low ouiput voltage but very high
current. Had to repair the control PCB and it turns out the 'solid state relay, SSR' was faulty. Bought a new one popped it in and away it went.
Bought it for $3.27 NZD, about $2.50 US so hardly breaks the bank. Has input sensitivity of 1mA with output capacity in the tens of mA and on
state resistance of 25Ohm AC and 3 ohm DC. Very useful and sensitive enuf to make your design task a little easier.

Check it out...LH1540....6 pin DIL IC

Craig

Let's forget the relay for the moment. I'm not sure if the following schematic works?
https://karusisemus.files.wordpress.com/2016/07/sch.png



The PC817 is replaced with 4N35, because I got some spare 4N35.
I have made the board with components soldered, but didn't work...

Hi,
the circuit diagram certainly looks like it should work.

Do you have a multimeter or better yet an oscilloscope?

Check for Vcc and Vdd on the board to start with.

Just as a matter of interest how did you make your board?. I note that its double sided and plated thru holes are not an easy proposition
for a hobbyist. Not unreasonable to whip around with your multimeter set on 'continuity' and check any thru holes.

Craig

Hi Craig,
            I will check the VCC and VDD later with multimeter, might get a Oscilloscope soon since I'm doing a lot of electronic project recently.
I use Diptrace 2.4.02PCB software, double sided works quite well in diptrace but not single layer, I tried before and was rejected by the pcb manufacturer 5 times due to short circuit. Single layer still works depend on complexity.

The pin 7 of 6N137 meant to be NC, is this correct?


checked Vcc Vdd Gnd1 Gnd2 in Diptrace schematics, looks alright..:

Hi,
do you mean you got a PCB manufacturer to make your board? If so then could probably guess that the vias are intact.

You need to recognise that you have two different earths. To measure a signal you must reference to its correct earth.

Yes, pin 7 of the 6n137's is non connected.

Craig

Yes there are vias intacted.
Yes I'm aware there are 2 separate power supply VCC and VDD, gnd 1 and gnd 2.

What should the value of VDD be? 7v?