Need help reading a schematic.

[Spork Schivago]

Hello,

I'm trying to learn how to build circuit boards. I ordered a kit off the net for a digital timer. Essentially, it's powered by a PIC and it has an LCD screen that gets connected to it. You program an amount of time and then it will provide power to another board that has a bunch of UV LEDs on them. You just use transparencies and photoresist boards with this kit and you get real nice circuit boards I guess.

Anyway, I've downloaded Eagle and I'm trying to create a schematic for the timer board. The guy who sells the kits provide schematics and board layouts, but they're all in PDF format. Eventually, I'd like to modify the design a bit so the power supply and the timer are all on one board.

I'm having trouble reading the schematic though. I've attached a copy. They use some different symbols, European ones I think they are. But I have a few questions I was hoping some one could help me out on. On the potentiometer located at A-6 (upper right corner), I see there's a pin that says S CONTRAST. And a bit further down in the schematic (B & C 4 - 5) there's some screw type connectors (to hook wires up to) that say X3-2 and X5-2. They both say S. Does the potentiometer go to both of those S's and to CONTRAST on the 16-pin header for the LCD screen?

Also, for X3-1 and X5-1, do I just tie them together because they both say O and then send them off to the PIC where it says K1 and K2? And what does the P stand for under K1 and K2? Is that just the power to the relays?

Any help would be greatly appreciated. Thank you.

[budm]

Re: Need help reading a schematic.

The wiper of the pot P1 pin S (net label named 'Contrast') is connected to the LCD1 connector pin 3 (net label named 'Contrast'). As you can see there are only two net label with the same name 'Contrast' so those to are electrically connected together. You should learn more about net label to understand what it is and what it is used for in the schematic.
Do not get confuse between the component pin names with net label.
For example the pot P1 as shown in the diagram, there are 3 electrical pins: pin 'A', pin 'E', and pin 'S'.

'Also, for X3-1 and X5-1, do I just tie them together because they both say O and then send them off to the PIC where it says K1 and K2? And what does the P stand for under K1 and K2? Is that just the power to the relays?'
'do I just tie them together' No.
Relay has 5 pin names: Pin '1' and Pin '2' are for the relay coil, then there are 3 pins for the relay contacts, Pin 'P' is the Common pin, Pin 'O' is the Normally Closed contact, pin 'S' is the normally OPEN contact. When the relay is energized, the pin 'P' will then make contact with pin S', pin 'O' is then no longer make contact with pin 'P'.

[Spork Schivago]

Re: Need help reading a schematic.

The wiper of the pot P1 pin S (net label named 'Contrast') is connected to the LCD1 connector pin 3 (net label named 'Contrast'). As you can see there are only two net label with the same name 'Contrast' so those to are electrically connected together. You should learn more about net label to understand what it is and what it is used for in the schematic.
Do not get confuse between the component pin names with net label.
For example the pot P1 as shown in the diagram, there are 3 electrical pins: pin 'A', pin 'E', and pin 'S'.

I gotcha Budm! I am a little familiar with net names and that's where my confusion came from. I thought there where two separate net names, S and CONTRAST. Like the potentiometer was connected to both signals. Does that mean for the stuff down by K1 and K2, they're just pin labels as well? The O, S and the P? Would they just be the labels for NO, NC and COM? The relay's are JS12N-K 1 pole power relays.

I'll do a bit more research on the net labels as well. Thank you!!!

[redwire]

Re: Need help reading a schematic.

It's a bit of a Euro schematic - and some people like to run wires all over and some like to use Nets.

I think you are getting mixed up with component pin names and net labels. Also Belgium has three official languages: Dutch, French, and German so abbreviations are tough to figure out. You would have to ask what "S" and "O" mean in that language.

The contrast pot has pins A,E,S (in English usually CW clockwise, CCW, wiper/slider) and the wiper pin "S" goes to Net CONTRAST which only goes to the LCD header pin 3. So the pin name "S" and Net name "CONTRAST" are connected to each other.

The relays have pins O,S,P (in English NC, NO, COM) and here the "S" pin goes to connectors X#-2. It has no connection to the "S" pin on the trimpot because they are different components.

PIC K1 and K2 Net labels (signals) only go to the 1k resistors. Their (Net) name is confusing with components K1 and K2 and not the clearest way to do a schematic.

The common terminal on the relays "P" go to connectors X3-1 and X5-1 only. Not the PIC - you don't want the PIC getting high power going to its pins.
Resistor R2 sets backlight LED current but has no value.

[Spork Schivago]

Re: Need help reading a schematic.

It's a bit of a Euro schematic - and some people like to run wires all over and some like to use Nets.

I think you are getting mixed up with component pin names and net labels. Also Belgium has three official languages: Dutch, French, and German so abbreviations are tough to figure out. You would have to ask what "S" and "O" mean in that language.

The contrast pot has pins A,E,S (in English usually CW clockwise, CCW, wiper/slider) and the wiper pin "S" goes to Net CONTRAST which only goes to the LCD header pin 3. So the pin name "S" and Net name "CONTRAST" are connected to each other.

The relays have pins O,S,P (in English NC, NO, COM) and here the "S" pin goes to connectors X#-2. It has no connection to the "S" pin on the trimpot because they are different components.

PIC K1 and K2 Net labels (signals) only go to the 1k resistors. Their (Net) name is confusing with components K1 and K2 and not the clearest way to do a schematic.

The common terminal on the relays "P" go to connectors X3-1 and X5-1 only. Not the PIC - you don't want the PIC getting high power going to its pins.
Resistor R2 sets backlight LED current but has no value.

Thanks! So the K1 and K2 on the PIC go to the K1 and K2 net names on the 1K resistors. It is a bit confusing, because the relay's have names called K1 and K2 on the board layout but the schematic is using K1 and K2 as net names and the PIC has a K1 and K2. A bunch of K1 and K2's! Thanks for all the help guys!

[Spork Schivago]

Re: Need help reading a schematic.

R2 is a 16 ohm resistor. I don't know why the value isn't listed on the schematic.

[budm]

Re: Need help reading a schematic.

The output of the PIC PIN 2 net label K1 goes to the resistor R3 on the leg the resistor with net label 'K1' to turn on the the Transistor Q1 which drives relay K1 coil.
Pin 1 net label 'K2' of the PIC goes to R4 to turn on Q2 which drive K2 coil.
You have component designator, I.E.: K1, R1, C1, etc.

[Spork Schivago]

Re: Need help reading a schematic.

Thanks BudM. And then does one of the relays power the voltage regulator IC2 (7805) to provide the 5V that drives the LCD screen? Or am I way off on that?

[budm]

Re: Need help reading a schematic.

Thanks BudM. And then does one of the relays power the voltage regulator IC2 (7805) to provide the 5V that drives the LCD screen? Or am I way off on that?

No.

[Spork Schivago]

Re: Need help reading a schematic.

Okay, I think I got it. The relays power the UV LED boards. I don't know what I was thinking thinking that they powered the voltage regulators. I still got a long ways to go with learning this stuff but I figured this would be a good schematic to test my knowledge with. Hopefully, one of these days in the near future I'll be able to not only fully understand it, but also be able to modify it a bit.

[Spork Schivago]

Re: Need help reading a schematic.

I think I understand it a bit more now. Voltage comes in from the house at the X1-1 and X1-2 connector. It goes through the bridge rectifier B1 (B80C800DIP) which converts it from AC to DC using 4 diodes. It then powers the IC1 7812 voltage regulator which in turn powers the IC2 7805 voltage regulator. 7805 produces 5 volts and powers the PIC on pin 14 and also powers the LCD screen on pin 2 and pin 15. Pin 2 on the header is for the LCD's VCC, Pin 15 is for the LCD's backlight. It also provides 5V to the POT, which in turn controls the resistance going to the CONTRAST net on the connector that goes to the LED. Looks like the voltage regulator IC2 (7805) also powers the speaker there.

Is this right so far?

[keeney123]

Re: Need help reading a schematic.

You'll get just hang in there. You have some good teachers. Are you using wire wraps or soldering?

[Spork Schivago]

Re: Need help reading a schematic.

Thanks! What the heck are wire wraps? I have a soldering station and solder components. I soldered all the components on the timer board already using my Weller. When I was younger, I had the hardest time soldering! I never had any teachers or anything. I had to learn it all myself until I found this place. It was insane, I tried adding solder to the iron and then touching the iron to the components (you can do that with SMD type stuff now a days but back then, it didn't work worth a darn!). I tried warming up just one terminal and adding solder. I gave up many times before I realized you had to touch both the pad and the lead at the same time and then apply solder!

A lot of great teachers here.

[Spork Schivago]

Re: Need help reading a schematic.

Are you talking about stuff like this?

https://upload.wikimedia.org/wikiped...ormat_1977.jpg

That's freaking old school! Wow. Do people still do that stuff? I got an old tube amp I'm supposed to fix for my buddy that's wired that way.

[budm]

Re: Need help reading a schematic.

Do you have the wiring diagram that shows how the board is connected to the rest of the stuff?

[stj]

Re: Need help reading a schematic.

Are you talking about stuff like this?

https://upload.wikimedia.org/wikiped...ormat_1977.jpg

That's freaking old school! Wow. Do people still do that stuff? I got an old tube amp I'm supposed to fix for my buddy that's wired that way.

lol
that's a VERO-pen / RoadRunner.
not seen that shit in decades!

[Spork Schivago]

Re: Need help reading a schematic.

Do you have the wiring diagram that shows how the board is connected to the rest of the stuff?

Like how the timer board hooks up to the power supply and the UV LED PCB? Or do you mean a board layout for the timer board? I just looked on the site for a hookup diagram, that shows how the timer board connects to the UV LED board and to the power supply. I found one. Here's a link to it:

http://www.e-stynus.com/index.php?ma...umentation&p=8

I've also attached a copy of the picture so you don't have to leave this site to see it.

I've also found on the site a picture of the board layout in what appears to be Eagle.

[Spork Schivago]

Re: Need help reading a schematic.

lol
that's a VERO-pen / RoadRunner.
not seen that shit in decades!

Wow, if you've seen that stuff before, you must be really old! Or maybe you just have experience working on older stuff. By most people's definition, I believe I'm what they call a youngin'. 34 years old (soon to be 35 in a few more months).

[rhomanski]

Re: Need help reading a schematic.

Seen it? I've got the tools and wire to do it. A lot of old Pioneers from the seventies have wiring done that way. I try to keep them like original. I'm afraid sixty is getting real close in my windshield.

[budm]

Re: Need help reading a schematic.

Like how the timer board hooks up to the power supply and the UV LED PCB? Or do you mean a board layout for the timer board? I just looked on the site for a hookup diagram, that shows how the timer board connects to the UV LED board and to the power supply. I found one. Here's a link to it:

http://www.e-stynus.com/index.php?ma...umentation&p=8

I've also attached a copy of the picture so you don't have to leave this site to see it.

I've also found on the site a picture of the board layout in what appears to be Eagle.

So you already bought the kit? It comes with step down power transformer?