Build your own Circuit Board

A "new fashioned" televisor, using an Arduino to drive the motor and display.

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Re: Build your own Circuit Board

Postby Andrew Davie » Sat Jun 03, 2017 3:41 am

With the lot. This is double-sided. IRF540 should be an IRL540, and probably a few errors here and there. I wanted to get something "complete" - now to analyse/debug it before I consider making a board. Still, it looks like a circuit.. never thought I'd be making my own :)

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Re: Build your own Circuit Board

Postby Andrew Davie » Sat Jun 03, 2017 4:48 am

Tried to minimise the footprint of the board. Still has the laying-down TIP31, but otherwise fairly compact. I spent hours and hours playing with routing. I must move on to other stuff soon.... still some errors here, though - will fix/update as I find them!

routing9.png
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Re: Build your own Circuit Board

Postby gary » Sat Jun 03, 2017 2:50 pm

Looking good, I like the nice chunky traces - I see one trace fouling a pad, and at least in one area the traces are too close together - the etching tolerance cuts both ways for home jobs.

But as you say. you are probably aware of those - looking good.

Have you decided on the etchant yet? They all work. I was surprised how well the peroxide hydrochloric combo works - but you do have to take more care - cheap as tho' and quick!

Edit: I don't think I have ever done a double sided at home, plenty and more in the lab but not at home - so you will be one up on me.
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Re: Build your own Circuit Board

Postby Andrew Davie » Sat Jun 03, 2017 4:30 pm

A bit more optimisation and bug-fixing. I haven't really gone through this with any sort of care - I need to revisit the circuit diagrams (which ones exist, anyway - I can't find my final motor one on the forum...?) and have a look at what the actual hardware is doing, and make sure it's all correct. I think I have fixed all of the "too close" issues; the crossovers near top right of the arduino microcontroller are deceptive - that's a programming header sitting on top of the uC so there's no issue with intersection of traces.

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routing10b.png
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routing10c.png
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Re: Build your own Circuit Board

Postby Andrew Davie » Sun Jun 04, 2017 2:05 am

Here's version #2. I spent quite a long time with placement and routing. It's quite challenging, sometimes impossible to put things where I want them to be and still keep within the 2 layer paradigm. This is about as small as I think I can get it - about 65mm x 55mm. Not quite within the 70 x 50 I set as a goal, but not far off!

routing12.png
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I redid the schematic and checked the values against the actual hardware. All seems OK, but I'll give it a few days of revision before going out and getting the chemicals for purchase. I'll use whatever Jaycar have in stock.

Attached is a PDF of the schematic I did. OK, it's not pretty - still have L-plates on. But here for reference to see/understand what I've done. Suggestions for improvements welcome.

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Re: Build your own Circuit Board

Postby Andrew Davie » Sun Jun 04, 2017 3:51 am

Andrew Davie wrote:This is about as small as I think I can get it - about 65mm x 55mm. Not quite within the 70 x 50 I set as a goal, but not far off!


Couldn't let it go. Reworked for an hour or so and now it's within my target size - now 65mm x 49mm.

routing15.png
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Edit: Found a few 'bugs' with the "design rule check" tool in Eagle. Missing connections, etc. Now updated.
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Re: Build your own Circuit Board

Postby Andrew Davie » Sun Jun 04, 2017 11:26 am

Consider say, a capacitor with two traces on the top of the board - one for each pin. I etch my circuit board and drill the holes in the appropriate spots, and insert the capacitor leads, solder... all done. I'm confused as to how this works when I can't access the soldering location. For example, terminal blocks - these push down and mount flush on the surface of the board, so I can't access the trace to do soldering. How is this problem overcome? The only thing I can think of is pre-soldering the trace/hole, and "melting" the terminal block into place by pushing it down while the solder is molten. There must be something I'm missing!

Edit: I'm surmising that all holes are considered "through plated" so that you actually solder/make the connection on the back side of the board. So if this is the case, then I need to be able to somehow "through plate" my holes. Mmmh.
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Re: Build your own Circuit Board

Postby Andrew Davie » Sun Jun 04, 2017 8:20 pm

Rivets, apparently. This is how you 'homebrew' your own through-hole plating. And the idea of doing that for 80+ holes got unattractive real quick. I decided to have a look at online board-manufacturing and see how much it would cost - compared to my time. I found OHS Park which advertised three boards including shipping for US$31 or thereabouts, and that's well within my budget. I've gone through their ordering process, and really liked the simplicity of their order process. I just uploaded my Eagle "board" file and away it went, giving me the following views and explanation of what I'd get (screen grabs)...

This shows the final manufactured board as if you held it in your hand. Your design should show gold copper, purple mask, white silk, black drills, and the board outline.
BoardTop.png
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This shows the final manufactured board as if you held it in your hand. Your design should show gold copper, purple mask, white silk, black drills, and the board outline. Internal cutouts are indicated by a black outline but are not filled in.
BoardBottom.png
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Drills should show up as white circles on a purple background. We want a single merged drill file exported in Excellon or NC Drills format with 2:4 precision, absolute coordinates, and no zero suppression. We will merge multiple drill files into one file and only plate the holes which pass through copper. Drills smaller than our minimums will be increased to the minimum size. See the design rules. No overlapping drill hits. No blind or buried vias. Small slots and plated slots are not supported. See our slots page. No oval or other non-circular drills
Drills.png
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This layer should appear 'mirrored' as if you were looking down on it through the board from the top. We will place copper everywhere we see gold color on this layer.
BottomLayer.png
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Soldermask layers show us where to remove the purple solder resist. The gold-colored areas will be exposed on the final board, and purple areas will be covered.
TopSolderMask.png
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We will place copper everywhere we see gold color on this layer.
TopLayer.png
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We will ignore the portion of the silkscreen that extends beyond the board outline. We will automatically remove any silkscreen that crosses drilled holes or exposed copper.
TopSilkScreen.png
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This layer should appear 'mirrored' as if you were looking down on it through the board from the top.
BottomSolderMask.png
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So, I've ordered already - let's see how it turns out!

Here's the Eagle files I used - schematic and board... I hope there's no errors, but want to stop spending hours and hours on this, and since I've put an order in that pretty much puts a stop to rearranging the deck chairs.
ArduinoTelevisor.zip
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Re: Build your own Circuit Board

Postby Andrew Davie » Wed Jun 28, 2017 12:06 pm

My prototype circuit board arrived today! I do realise that there are bound to be errors and issues - but nonetheless I'm stoked. Looks fine, and I will populate it today and perhaps in a day or two will be able to test to see if it works :)

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Re: Build your own Circuit Board

Postby Andrew Davie » Wed Jun 28, 2017 1:14 pm

Populated. Everything fit perfectly!

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Re: Build your own Circuit Board

Postby Andrew Davie » Wed Jun 28, 2017 9:38 pm

I've started testing.

I wired in the motor, the SD-card (well, plugged in), and the IR transmit/receive. I connected my laptop too, so that I could see debug diagnostics. First issue was a "file not found" and "SD error" indicating problem with the SD reader. I was using a spare unit, but to be sure wiring was correct, I unplugged the unit I was testing with on the earlier version of the televisor and made sure the wires went to the correct places. Once that was done, another test and the Arduino is correctly talking to the SD card. So there might be a wiring mismatch in my design there. For now, it's fine with a few long wires and dangling. There's going to be a new version of the board anyway, to incorporate the LM317 power regulator.
Anyway, so now the SD is communicating, power up again and now the motor's spinning - wahoo! It didn't stabilise however, and tracked that down to the IR receive being wired backwards - well it should be wired backwards, but it wasn't, so it was backwards backwards which was wrong. Fixed that and tried again - now the motor comes up to speed, and the PID is obviously kicking in correctly.

Haven't tested the LEDs yet - this board is designed for a 12V LED array and my array is 26V. But I think the next step will be to just breadboard a simple 3-LED string suitable for 12V and see if I get some pulsing. Or, I could hook up my oscilloscope I suppose. Both easy tests.

I guess it's going OK so far. More to come.
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Re: Build your own Circuit Board

Postby Andrew Davie » Wed Jun 28, 2017 10:15 pm

More testing - all good!

I plugged in the Nextion LCD display and it's functioning correctly - it lets me select files from the SD card as designed. So, nothing to fix there (!) I wired up a 3-LED "matrix" on a breadboard. I didn't bother putting a resistor there because the board has a 16 ohm resistor already (and I calculated that at 12V the matrix would actually require a 9 ohm resistor). In the final build that 16 ohm resistor will be removed - but for now it's acting as a limiting resistor giving the LEDs something like 8 mA which means they're dim but nonetheless I could see if the circuit was working. It was (!!!) The speaker is also working.

So, it looks like EVERYTHING is functional, with the possible exception that I need to check the wiring on the SD connector; it might be inverted and so you can't directly plug the SD card in yet. But a few jumper wires and it's working. Pretty stoked this was so painless - and it's sooooo much smaller and neater now :) Next step will be building a nice 12V LED matrix board. Here's a video...


youtu.be/el4sQ4mGITg
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Re: Build your own Circuit Board

Postby Andrew Davie » Wed Jun 28, 2017 11:20 pm

More testing. Problems.

Although it seems functional, there are a few issues that have come to light after a bit more testing.

1) I put the oscilloscope on the sound output and it's extremely 'noisy' even when there's nothing being output.
2) The IRL540 which should be cool (as it's being driven at 0V or 5V by the PWM) is actually extremely hot.

So, there's a few things wrong at least. I will start tracking these down on the weekend, I guess.
Strange that it appears to be functional, but not behaving the same as the original. Hmmmm.
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Re: Build your own Circuit Board

Postby Klaas Robers » Thu Jun 29, 2017 5:57 pm

Have you inserted a suitable low pass filter in the audio output circuit? When you use PWM for audio there is maximum high frequency activity at no sound output (silence). You can't hear it, but it is there. You see it on your scope and you feel it on the transistor. Full power ultrasonic output.
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Re: Build your own Circuit Board

Postby Harry Dalek » Thu Jun 29, 2017 5:58 pm

Very impressive Andrew and i like your test :wink: program
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