pc817 optocoupler - Page 1
Forum section: electronics / beginners

author: glinjik
author_rank: Regular Contributor
timestamp: January 23, 2020, 10:40:01 am
content: hi i have a little confusion the pc817 shown in this diagram appears to be backwards ie if i use it in the manor shown i would have to put it on the back of the board to get the orientation correct? are there different variants of this chip the one i have is pc817x i also have el817 also is it necessary to cut an isolation slot under the chip and further i see it has a isolated ground? is this back to the bridge rectifier as opposed to ac mains ground, first time im using this chipthe fist picture is in the circuit the second is a pinout i got on google

author: fourtytwo42
author_rank: Super Contributor
timestamp: January 23, 2020, 11:02:00 am
content: To many questions in one post but the answer to the first one is your schematic only has a functional symbol for the part with no pin numbers so you simply match the function to the pin, eg emitter is pin 3. There are not different 817's with different pinouts.

author: glinjik
author_rank: Regular Contributor
timestamp: January 23, 2020, 11:10:48 am
content: thank you but i am still miffed to get the orientation correct i would need it under the board so pin 3 goes to top

author: hsn93
author_rank: Regular Contributor
timestamp: January 23, 2020, 11:46:14 am
content: to validate your point, you actually have to take picture of the actual board / pcb design not the schematic

author: austfox
author_rank: Regular Contributor
timestamp: January 23, 2020, 11:53:04 am
content: You are getting confused between the schematic and PCB layout.Schematic usually has positive at the top and negative at the bottom, mainly for ease of interpretation. When it comes time to design the PCB, you can place your voltage anywhere, your components anywhere and in any orientation.Keep your optocoupler on the top side with the rest of the components, just ensure the traces between components connect to each other correctly.

author: glinjik
author_rank: Regular Contributor
timestamp: January 23, 2020, 12:00:25 pm
content: this is the bit in question i understand what you mean but it would mean putting jumper wires to get it into the correct orientation maybe it was done for ease of schematic rendering a bit like a 555 timer where the digram is nothing like the orientation of the legs but i don't suppose it would hurt putting it on the bottom of the board?

author: hsn93
author_rank: Regular Contributor
timestamp: January 23, 2020, 01:30:24 pm
content: Quote from: glinjik on January 23, 2020, 12:00:25 pmthis is schematic again, the orientation doesn't matter (its for connection and reading).the orientation + jumper + how its mounted on board = pcb board design.schematic can even have wires crossing each other:the schematic doesnt have to fit actual footprint.. look at diodes for example in the schematic they are 2 pins but they can be 3:pcb layout:

author: glinjik
author_rank: Regular Contributor
timestamp: January 23, 2020, 02:24:35 pm
content: Thank you yep its clear now i kinda like laying out the board like it is in the diagram don't know but i do maybe just inexperience i Dasent matter so much i really am experimenting to figure out how it works more than a finished product I've not played with smps before i finished the choke yesterday 219vdc that had me panicking a bit but didn't go bang i ha dent thought when i started this project how much voltage was going to be fed in with a transformer 240vac in 19 v out nice and safe but 219vac different ball game i won't be handling this thing when its powered up like i did with the linier supply

author: austfox
author_rank: Regular Contributor
timestamp: January 23, 2020, 02:41:34 pm
content: Put this together real quick with auto-route, but you will get the idea...

author: glinjik
author_rank: Regular Contributor
timestamp: January 23, 2020, 02:56:24 pm
content: thank you so much very helpfullQuote from: austfox on January 23, 2020, 02:41:34 pm