I’ve decided that I’d like to take the schematic and board design a user posted in PDF format and make it an Eagle file so I can modify it a bit. It has a PIC and I really have no experiences with PICs as of yet. I’d like to learn about them though in the future. Anyway, I created the schematic in Eagle and then routed the board in Eagle. When I run the checks on the schematic though, I get an error saying the PIC’s VSS is connected to GND and the PIC’s VDD is connected to +5V. If I add the symbol for VDD and VSS though, on the board, I cannot connect it to the +5V and GND nets. Is there away to connect those VSSs and VDDs to +5V and GND? Or can I just safely ignore the error? Thanks!
Thank you for responding Ross Robotics. There’s a couple other problems that I don’t know how to fix (I don’t even know if there is a fix). The PIC has two pins that aren’t needed. From what I’ve read, there’s no No Connection symbol / device in Eagle. I’ve seen some people tie these to GND but I don’t know enough about PICs to know if that’s a good idea or not. I’m guessing PICs can be used in multiple modes and perhaps grounding a couple of the pins throws it into some unwanted mode for me or worse yet, damages the chip because of the mode I have it in.
I realize that this is just weirdness with the auto-router, but there are 2 +5v traces connected to pin 1 of C5. There should be a single trace that goes from C5: pin 1, to R2: pin2, and then to IC3: pin 14.
Ross Robotics:
VDD is postive supply and VSS is negative supply. So, those are correct.
How are you going to program the PIC? Right now you don’t have an ICSP header for in-circuit programming.
It came pre-programmed. I want to modify the software on the PIC when I learn how to program them. The code he posts is in BASIC but I’d like to write it in C (my native language ). If I added an ICSP header for in-circuit programming, would I hook something like a Microchip PICkit ICSP programmer to the ICSP header when I wanted to program it? Would I need to somehow switch the PIC into programming mode? Thanks for all the help. Still very knew to all of this and I’m sure some of my questions are very simple to the users on this forum. I really appreciate all the friendly helpful help.
I’m a bit confused about pin 12 and 13 on the PIC. They’re currently connected to the data lines for the LCD display (it’s in 4-bit mode, not 8-bit). Pin 12 is data line 6 and pin 13 is data line 7. According to this diagram ( https://en.wikipedia.org/wiki/In-system … c_icsp.jpg ), I’d need to hook pin 12 up to ICSPCLK and pin 13 to ICSPDAT. If I was programming the PIC, could it cause damage to the LCD? Or would it be safe?
davep238:
I realize that this is just weirdness with the auto-router, but there are 2 +5v traces connected to pin 1 of C5. There should be a single trace that goes from C5: pin 1, to R2: pin2, and then to IC3: pin 14.
Thank you for the reply. That's the way the original was routed. I copied his design. So I route C5: pin 1 to R2: pin 2, like it's currently routed, and then what do I route to IC3: pin 14? R2: pin 2 to IC3: pin 14, right?
davep238:
I realize that this is just weirdness with the auto-router, but there are 2 +5v traces connected to pin 1 of C5. There should be a single trace that goes from C5: pin 1, to R2: pin2, and then to IC3: pin 14.
Thank you for the reply. That's the way the original was routed. I copied his design. So I route C5: pin 1 to R2: pin 2, like it's currently routed, and then what do I route to IC3: pin 14? R2: pin 2 to IC3: pin 14, right?
Can I route R2: pin 2 to IC3: pin 14 like this? (I’ve attached a zip file).
Also, I’ve tried to add some pins for an ICSP header. I see the datasheet for the PicKit3 shows that I should have a resistor between VPP and VDD. It says, A pull-up resistor (typically around 10 kohm)
is recommended to be connected from the VPP/MCLR line to VDD so that the line may
be strobed low to reset the device.
How does this look? Is there a specific header I should be using? From the data sheet, it almost looks like they have 6 pins in a straight row but on the net, I see people are using the 2x3 header. Thanks guys!
Also, on the schematic, I can safely ignore the two errors, right?
POWER pin IC3 VDD connected to +5V
POWER pin IC3 VSS connected to GND
I understand that the VDD is equivalent to positive and VSS is GND, but in Eagle, I see there’s actual VDD and VSS symbols in the schematic. I just can’t tie them to the +5V and GND lines.
Thanks n1ist. I have modified the design. I’m worried about the resistor that I added though. I don’t know enough about circuits yet to tell if it will affect the other components. I’m pretty sure it’ll only affect the data going to the ICSP pins though. Here’s an updated version but now I get a DRC Drill error on my via. I don’t know how to fix that.
Spork Schivago:
Thanks n1ist. I have modified the design. I’m worried about the resistor that I added though. I don’t know enough about circuits yet to tell if it will affect the other components. I’m pretty sure it’ll only affect the data going to the ICSP pins though. Here’s an updated version but now I get a DRC Drill error on my via. I don’t know how to fix that.
You got the DRC drill error because the via's drill diameter is slightly less than the DRC's minimum drill size. One way to fix this is click on Edit -> DRC -> Sizes: change minimum drill from 24 mil to 23 mil. The other way is to change the size of the via's drill to 24mil. Type the following into the command line: "ch dr 24mil" (without quotes). Press the enter key and then click on the via. "ch" is shorthand for "change", and "dr" is shorthand for "drill".
Oh, cool! Thank you! I wish I didn’t have to use the via but I think in order to not use it, I’d have to reroute it totally different. Maybe move some components around a bit. Does the “change” command persist through restarts of Eagle or will I have to change the drill size every time I start a new project and use a Via? I tried finding where it stores the default value and couldn’t find it anywhere under any of the menu options.
I’m worried about the 10K resistor attached between pins 1 and 2 on the ICSP header / pins. Is that resistor fine there? Or do I need to put it somewhere between the routes that go to pin 1 and pin 2?
Spork Schivago:
Oh, cool! Thank you! I wish I didn’t have to use the via but I think in order to not use it, I’d have to reroute it totally different. Maybe move some components around a bit. Does the “change” command persist through restarts of Eagle or will I have to change the drill size every time I start a new project and use a Via? I tried finding where it stores the default value and couldn’t find it anywhere under any of the menu options.
I’m worried about the 10K resistor attached between pins 1 and 2 on the ICSP header / pins. Is that resistor fine there? Or do I need to put it somewhere between the routes that go to pin 1 and pin 2?
The drill size doesn't seem to default to what I want either. There may be an EAGLE file where defaults are stored, but I don't know what it's named. I'm sure that someone will speak up about this.
As far as the resistor goes, you can leave it where it is, or move it to the left of the 6-pin header next to pins 1 & 2. If you move the resistor near the header, then you can just use a bottom (blue) trace to connect the PIC’s pin-4 to the header’s pin-1. Then use top (red) traces to connect the resistor to the header. Doing this eliminates the via.
You’re right, R5 doesn’t affect R2. You will need to solder R5 before R2 and the ICSP header because otherwise it will be difficult to solder R5 after those 2 parts are installed.
Thanks so much for the help and info! Originally, I tried putting the ICSP header over by where the text, “UV Exposure Timer” was because there was a good bit of room over there. It was just really hard to route the traces. I would of had to use a lot of VIAs or try and redo the other routes.
I’d like to eventually replace some of the through-hole components with SMD components. Like the transistors, the 10K trimmer resistor and some of the capacitors. I’m just not very good at calculating what wattage I need for the SMD components. For example, for R5, I picked an 1/8 watt 0805 package resistor. Could I of used a smaller package though without it getting too hot? Could I of went for a 1/16th watt SMD resistor there? I know this isn’t the place to ask questions like that and I don’t expect anyone to respond. It’s just stuff I still need to work on and figure out.
I think I understand the circuit a bit. Voltage comes in from the power supply at the X1-1 and X1-2 connector. It goes through the bridge rectifier B1 (B80C800DIP) which converts it from AC (if we’re using an AC power supply), otherwise, if I power it with DC, the polarity shouldn’t matter. It uses 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.
Spork Schivago:
Thanks so much for the help and info! Originally, I tried putting the ICSP header over by where the text, “UV Exposure Timer” was because there was a good bit of room over there. It was just really hard to route the traces. I would of had to use a lot of VIAs or try and redo the other routes.
I’d like to eventually replace some of the through-hole components with SMD components. Like the transistors, the 10K trimmer resistor and some of the capacitors. I’m just not very good at calculating what wattage I need for the SMD components. For example, for R5, I picked an 1/8 watt 0805 package resistor. Could I of used a smaller package though without it getting too hot? Could I of went for a 1/16th watt SMD resistor there? I know this isn’t the place to ask questions like that and I don’t expect anyone to respond. It’s just stuff I still need to work on and figure out.
I think I understand the circuit a bit. Voltage comes in from the power supply at the X1-1 and X1-2 connector. It goes through the bridge rectifier B1 (B80C800DIP) which converts it from AC (if we’re using an AC power supply), otherwise, if I power it with DC, the polarity shouldn’t matter. It uses 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.
You're right how the circuit works. The 0805 resistor is an easy one to hand solder. You will need at least a 15 volt power supply because the 78xx regulators need at least 2.5 volts more than the output. I looked up the Omron G6RW relay and didn't find it in the Omron catalog. Instead, use the "G6RN-1 12DC" relay. An SMD equivalent of the BC547 is the BC847. The 100nF caps (through-hole) can be 50 volts, 100 volts is overkill. The 100nF caps can be replaced with SMDs. The 0805 package is a nice size to hand solder. Also, C4 is not needed, since it duplicates C3. If a 5 volt relay is used instead of the 12 volt relay, then the 7812 is not needed. I've attached a ZIP file of the schematic and PCB using SMD parts (except for R2) and 12 volt relays.
Wow! That’s freaking awesome Dave! Thanks so much!!! The original schematic (in PDF format) showed he used a G6RW for the relays but when I ordered the kit, it actually came with two JS12N-K. I have the 15 volt power supply.
If I understand this correctly, the relays are what provides power to the UV LED boards. There’s 12 of them, 100mm x 100mm each. Essentially, you daisy chain them together to get one big top board and one big bottom board, each 200mm wide by 600mm long. There’s 32 LEDs per board. Do you think using a 5 volt relay would be enough?
I have a basic understanding of relays. They’re essentially a switch, right? So a 5v relay can handle a maximum of 5 volts, right? I really appreciate all the help you’ve provided. It’s great that I actually understand parts of the circuit. Still get a bit confused with the transistors and the relays though. I really struggle with transistors. I’ve read a lot about them but the documents are really confusing. They talk about holes and things like that. They talk about how they can be used as a switch or an amplifier. NPN, PNP, emitters, collectors, bases and all that stuff, just a bit confusing.
). If I added an ICSP header for in-circuit programming, would I hook something like a Microchip PICkit ICSP programmer to the ICSP header when I wanted to program it? Would I need to somehow switch the PIC into programming mode? Thanks for all the help. Still very knew to all of this and I’m sure some of my questions are very simple to the users on this forum. I really appreciate all the friendly helpful help.