Kind ofhard to hep without knowing what'swrong Care to enlighten us ?
I've checked the followingComp/Pins = VLow / VHighU3/5,4 = 0.00v / 5vU4/5,4 = 1.5v / 1.5v
I can't help you if you only give me partial information.This:doesn't tell me nuch except that U3 is OK.as far as U4, I need the followingR3 voltage dropU4-1= ___U4-2= ___U4-3='X Don't Care'U4-4= ___U4-5= ___U4-6=___ (transistor base test input, used to test transistor irrespective of led)Conditions:All supply voltagesJP1 SWITCH POSITIONALL INPUTS ON ALL INPUT CONNECTORSJP1JP2JP3Air Assist Switch PositionTo be honest, I'm afraid to ask why you don't just test U4 on a bench with a solderless breadboard.It's not rocket science.
R3 voltage drop = 0v (Why? Resistor still working but no V Drop?)
U4-1= 0.01v / 24.1v
I'm assuming you want all voltages from U4 relative to ground?
I asked for the voltage across this resistor.Please follow instructions and save your questions for later.This can't be correct.I did exactly that. Possitive probe on 24v Variable input and neg probe on U4-Pin1. Reading 0v across it...Simulated the circuit in http://www.falstad.com/circuit/Kept getting a nan infinite matrix error until i put a diode between R8 and R4...Look at the schematic.Pin-2 is connected to GND.U4 is an opto coupler so Pin-1 is the anode.Leds have an intrinsic forward voltage. The voltage drop across a led inside an opto is the same as the voltage drop across any led.Put a led in a solderless breadboard and connect the same value current limit resistor as R3and then apply power and tell me the voltage on the ANODE of the led.Voltage drop across R3 should be 23.4v i know that it should...What is the voltage on the ANODE of the led ? (with the CATHODE connected to GND)IT CANNOT POSSIBLY BE THE SAME AS THE POWER SUPPLY !I kid you not 24v running from pin1 through pin2 to ground....That's Electronics-101.Something is wrong with the information you are giving me or the led is OPEN (damaged)Seems likely to be the cause. I have one left thats still in packaging. What specs do i need to be paying attention to so that i don't pop this one? SpecificationsIf you tested the transistor like I said you would know that works.Plugged it into my DMM and reading a clear 245 same as all 2222n's i have so either i got a box of duds or its fine.If the led is damaged then U4 is bad and must be replaced.There are no other possibilities.Yes, of course. I also don't want U4-4 connected to tha Nano.Remove that connection and connect U4-4 to GND.Never connected just did that as an example. There is no nano in this circuit.
"I kid you not 24v running from pin1 through pin2 to ground...Obviously, if the led is OPEN , and the voltage across R3 is 0V (24V/24V=0V) then the currentthrough R3 =0A and there CANNOT be ANYTHING"running from pin-1 THROUGH pin-2 (where theOPEN led diode is ) to ground , because there ISno connection BETWEEN pin-1 & pin-2.Across* would have been the correct word. I got ohms law down its just terminology about places on the circuit that i get lost on.Eg. Across, through, within. Especially when im trying to do it at 3am... And I told you to breadboard an led and resistorand report the voltage on the ANODE of theled with the CATHODE connected to ground.When you complete your homework I'll answermore questions and not before.I though i put that in my reply.. Voltage across the LED+R is going to 24v... Because thats all the voltage there is...Led Vd should be around 1.7v to 1.8v... standard for most LEDsR Vd should be 22.2vIs this simulation incorrect? Its showing only 0.5v across the optos LED... "Would it be safer to add a diode on U4-Pin5 to ground so as to avoid any backvoltage?"What does a diode on the collector of an optoon the output side of a 5000V ISOLATION barrierhave to do with protecting a led on the OTHERside of the 5000V ISOLATION barrier ?My thought regarding this would be because of the two input voltages... The opto has an output Emmiter-Collector breakdown voltage of 7v. Even though they share a common ground could the "ON/OFF feedback" from the the solenoid at 12v not overpower the 5v input and cause a reverse voltage? So if somehow 12v gets grounded even for a second they would be a +7v diffence?
Post the corrected schematic."R3 voltage drop = 0v (Why? Resistor still working but no V Drop?)""Voltage drop across R3 should be 23.4v i know that it should...""Led Vd should be around 1.7v to 1.8v... standard for most LEDsR Vd should be 22.2v"All of those statements are yours.Why is the second one wrong?(24V-1.8V=22.2V)The second one refers to the simulation. Opto input side registers as 0.5v on the probes in the sim. Cannot set variables of optocoupler... So it was an assumption.Very hesitant to connect my final opto to the Breadboard without ensuring i've got it right...So from the spec sheet.Max Vf = 1.7v (Is this the max V before it goes pop?) Im being really special atm... So Vf = Vd = VfdMin Vf = 0.9v (Is this the minimum V before it turns switches on/off?)Max If = 50mA (Max = gets hot/goes pop!) You can reduce R3 to 1.8k or 2.3k to increaseU4 led current.Ok i think i got you... current would then be (24-1.7) / 1800 = 0.012A (24-1.7) / 2300 = 0.009ASo (24v-1.7v)/0.05A = 446Ω Absolute Minimum for 24v -> U4-P1???"Is this simulation incorrect? Its showing only 0.5v across the optos LED... "You tell me. If the led forward voltage is 1.8V, would it be on at 0.5V ?So if im right, Which im probably not. Shocked but glad you've stayed to help...With the specs of Vf Min = 0.9v = LED switch point?