1
\$\begingroup\$

I'm an amateur 3D printed Robotics maker (youtube.com/PatchBOTS). I come at this from the 3D printing/engineering side and I'm learning the electronics and coding as I go. Up till now I've been buying prefab boards and wiring them together or making my own little circuit boards on solderable breadboard/scratch board type pieces. i'm at a point now where I want to learn how to make my own circuit boards to save space/time/etc. I have never one this before, butenter image description here I have a copy of Autodesk Eagle and been following Jeremy Blums tutorials, but I have still run into issues I was hoping you could help with.

I'm making a Star Wars blaster gun. It has two triggers: 1. Single Shot trigger--> sends ground signal to soundboard pin0, also sends ground signal to base of PNP which activates the LED at the end of the barrel. 2. Multi Shot trigger-->sends ground signal to soundboard pin1, also sends ground singla to base of PNP which goes to pin8 of a 555 timer which blinks the same LED in sequence with the sound. This is controlled with a 1k variable resistor.

I want to make a board out of this, but I'm running into some issues. 1. How do I denote a "pinout" I basically want through holes at the end of the board for all the black text in the image. I'm not sure what to put there for "leaves board here". 2. How do I add the variable resistor along pins 6,7,8. The 555 timer is out of order and I have no idea how to even add in a variable resistor. 3. Other than my two problems, can you see anything else wrong with this schematic. I'm very new to this and I'm sure I have something backwards or upside down. Any help would be appreciated. Updated Schematic EDIT: I've update the schematic to show the HEADERS recommended by others! Thank you guys! What about the variable resistor? How can I set that up along 3 pins that aren't near each other? Schematic3

EDIT2: I think I have the variable resistor figured out. WI think this is right? Can anyone see anything jump out at them?

\$\endgroup\$
  • 1
    \$\begingroup\$ 0.1in headers work well for this. You can use a single multi-pin header or many 2 pin headers. \$\endgroup\$ – vini_i Jul 26 '18 at 23:57
  • 1
    \$\begingroup\$ If you want to use a connector, I'm sure the Eagle libraries have lots of connectors that you can explore :) Search up what they actually look like on Digikey, or check out the 3D models if your copy of Eagle has that all set up. Otherwise, +1 for 0.1" headers. \$\endgroup\$ – Daniel Jul 26 '18 at 23:59
  • 1
    \$\begingroup\$ "headers" i think that was the missing term I was looking for. Thanks guys! I"ll update hte schematic. \$\endgroup\$ – PatchBOTS Jul 27 '18 at 0:03
  • \$\begingroup\$ I think you either have a wire shorting your D3, D4, or they are placed in wrong direction. Also your schematics will be much easier to follow if you use net labels on collector and R4, for clean separation of input part from logic part. \$\endgroup\$ – Maple Jul 27 '18 at 1:14
1
\$\begingroup\$

If you want a group of header pins (through holes) to end up together on the board, consider using a single header with more pins.

You show your schematic here, but not your board view. The schematic should be arranged so as to make the circuit as easy as possible to understand in function. This is why the pins on the 555 timer are differently ordered. The board view is where you actually arrange components, draw circuit board traces, etc. In board view, eagle will show rough physical sizes of components, what will be printed on the circuitboard (in ink), and it will automatically connect the pins of all of your added devices with "airwires" which are just little yellow lines that show every connection on the board. You then position components and replace the airwires with circuitboard traces using the routing tool. If you don't want to manually draw your circuit traces, or it's too difficult to figure out, you can use the autorouter, which will find a solution to the board based on parameters you set, although most humans find they can outperform the autorouter in both grace and practicality. I like to use it to solve overall plans or tricky parts, and then replace it with my own more graceful traces. You end up with something like this:

circuitboard layout

You can see 2 teal dots on the LM393N chip, these are vias (connections from the top to the bottom of the circuitboard) that I haven't yet found a way to avoid without perturbing more important parts of the board. I ended up selecting acceptable vias, and also selecting the location of these, based on autorouter solutions.

The inductor shown on the circuitboard is not the one I will be using, but it has a matching pin arrangement and rough size. I had to find it by manually going through every inductor in the catalog.

You can fish through the device catalog to find another variable resistor/potentiometer that has an adequately similar pin placement, and if that doesn't work there are tutorials on how to add components to your catalog (I added the MIC4428 shown)

One little trick I've found so far is when you first shift to board view, and your components are all jumbled together, drag them far apart and individually grab them, see what they're connected to, and try to shift things around to minimize the number of yellow lines that cross. For components that require short or wide traces, you can still prioritize them by putting them together on the board first before figuring out the rest of the jumble.

\$\endgroup\$
  • \$\begingroup\$ Very helpful, thank you! I haven't dived into the board portion yet. i suppose if I had a mistake I could always fix it in Schematic view, and then it will update in board view? I will keep all your suggestions in mind as I build out the board view. \$\endgroup\$ – PatchBOTS Jul 27 '18 at 1:14
  • \$\begingroup\$ You absolutely can. You will lose your routing (traces) to the components, but once you change the schematic, they will be reconnected with airwires and you can re-route them. Search the catalog for "variable resistor", "trimmer resistor" and "potentiometer" to find a catalog entity for your variable resistor. Make sure the catalog entities you select have comparable real life pin spacings to the components you'll actually use, or you'll have to go back and manually replace them. \$\endgroup\$ – K H Jul 27 '18 at 1:34
  • \$\begingroup\$ I actually found a library from the manufacturer of my exact one and it had it in there! So cool! I just did a trial run on the board and I'm finding little changes I can make (3 relevant header groups, instead of 9 individual or a big group of 9). Is there anyway to run some kind of simulation to make sure there are no mistakes? or is that just wishful thinking? \$\endgroup\$ – PatchBOTS Jul 27 '18 at 1:53
  • \$\begingroup\$ @PatchBOTS, Sparkfun's "According to Pete" series has some pretty good PCB tutorials on YouTube. I used them when I routed my very first board. EEVblog is also a good resource. If you have more separate questions about your design (schematic or layout), definitely post as a new question. Making your original question longer will make it harder to answer, and veers into "forum" territory, which is not what this site is about. If you ask a new question related to the same project, you can add a link to your first question to provide readers with clarification. Best of luck! \$\endgroup\$ – Daniel Jul 27 '18 at 4:02
  • \$\begingroup\$ @PatchBOTS if you mean you would like to simulate the circuit to confirm that it works, you certainly can, you just have to rebuild the schematic in a program like LTSpice(free), which has it's own learning curve (not too bad) and it will only take into account connection, it works on a schematic, so it won't tell you things like if your traces are too long or too thin or that you accidentally built an antenna. \$\endgroup\$ – K H Jul 27 '18 at 4:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.