Prototyping Board Jaycar

[Curtis Boykins]

Ibuilt a door alarm that used a Duinotech Leonardo Tiny Atmega32u4, an RGB led with resistors, an active buzzer module, and a thin film pressure sensor. I'd made a prototype on an Uno and breadboard before moving to the Tiny and a prototyping board.

I finished soldering everything today and as I began programming the functions I realised the green led pin (D10) wasn't functioning (it had been in the past). I used a multimeter and found that pin D9 had no power, despite being set to digital write High... D10 had 0.5v coming out, and D11 had 5v.

I checked continuity of all the different connections I'd made and couldn't detect any shorts. I unsoldered the wires from D9 and D10 just in case, but now the board isn't detected by my laptop. I'm wondering if I've damaged it in my novice heavy handed approach to electronics?

Without your wiring schematic, and a picture of your wiring, any advise given would be guess work! But the chip getting hot usually means you have a short circuit to ground somewhere! Probably on a GPIO pin.

If I have a short to ground, presumably the best way to check would be a multimeter with the - on the ground pin and to go around the other pins using the + probe to see if I get a circuit using the continuity mode? I tried that and didn't find anything so am going to wondering if I did something wrong?

Thanks Mike. I used the wrong words, didn't mean I had connected the I/O pins to ground... More that there are enough pins to connect to other sensors and modules that may in turn need more ground connections than there are pins.

Also when trying out some new hardware always put it the software first before removing the power attaching the hardware and applying the power again. Because you never know what the software originally in it programmed the I/O lines to be.

I had checked the LEDs as I went and that was fine, got a little confident and added the buzzer and pressure sensor at the same time. When I retry the circuit I will first check the pins of everything with the multimeter first.

Thanks for the photos but what we are missing is how you connected this to your Arduino. Especially the + signal, where was that on the board? Have you a photo of that.

Did you use header pins or did you just push the wires into the socket on the board?

The Arduino was attached to the board using a double sided sticky pad. I did wonder if perhaps that might have caused a short on the underside? There aren't any real places to screw it on, so I assume I need to glue it with a non-conductive adhesive, which I'd have thought the pad was...

The only other thing I can think of is that I had to bend the pins of the pressure sesor 90 degrees so that the board would fit horizontally. I'm assuming the board wiring isn't such that the force required to bend the pins would have created an internal short? I guess I will find out when I do some troubleshooting later.

For a while now I've been thinking about how to package FPGABee into a small case. It seems this is a step that many retro FPGA project's stop short off, but it's something I'd like to have a go at. The Nexys-3 board is an excellent development board but it's not very practical to setup and the soldered wires onto the PS2 keyboard socket keep breaking off.

In order to reduce the unknowns (ie: my soldering/PCB design skills) and help get this up and running, I also ordered some prototyping pieces including a "Stick-It" board and add-ons for VGA and PS2. Conveniently the Stick-It board supports the same Pmod connectors as the Nexys-3, so I should be able to re-use my existing PmodSD.

While waiting for the XuLA bits to arrive from the States I started on a case for it. It's a simple, but reasonably decent looking case from Jaycar and I've put in the VGA, PS2, speaker, power connectors and a power switch. There will also be a USB connector so the FPGA can be re-programmed without opening the case - this will either consist of a cable from the back panel to the XuLA, or I might try to redesign the PCB to have the XuLA's USB socket protrude through the back panel:

The front panel will consist of a couple of LEDs, reset button and the SD card slot. (Note that although the XuLA2 has an on-board SD card slot, I won't be using it once it's all mounted in the case).

I've also had a go at designing a custom PCB for it. I've deliberately designed it so there's no surface mount components so that construction remains simple, but includes VGA, PS2, speaker, support for 3 leds, 3 push buttons, connector for the PmodSD and some tiny prototyping areas.

I start with my circuit board. The best time to make your mounting board is when you are making your circuit ... before it's populated. Lay the drilled circuit board over the acrylic sheet and mark the outline and where the mounting holes should go. I usually try to make 4 mounting holes so that my board is stable, but sometimes 2 or 3 holes is all that you have room for.

Acrylic is usually sold with a protective plastic sheet on both sides, it is important to leave this on until you have completed the cutting and sanding of your edges. The plastic sheet will protect the acrylic from being scratched by tools while you are cutting/sanding it.

Cutting acrylic is not too difficult but care is needed. If you are using a circular saw or a jigsaw, slow and steady is the key. Too fast and the acrylic will chip, go too slowly and the waste will melt with the heat generated by the friction of the blade (not too hard to clean up, though a pain).You can also use a hacksaw with a fine tooth blade on it. I've also used the score and snap method, that is, score both sides of the acrylic with a craft knife (using a straight-edge like a metal ruler) and then place the acrylic over a sharp edge on the line of your cut, bend the acrylic and it will snap along the score.

However you cut the acrylic, I recommend trying it first before you commit to a final board. Also, the edge is likely to be rough ... a coarse sandpaper can be used to trim the acrylic, and then a finer sandpaper to make it clean and shiny. You can go down to a wet paper for a really glossy finish, if that's what you're into ;)

Using a 3mm drill bit, drill the holes for the bolts. You want to make the holes in your acrylic a tight fit so that when you screw the bolts in, they will cut their own thread into the acrylic. Again, I counsel you to try on a waste piece before committing to the final drill bit size.

Place the bolts through the mounting holes of your circuit board and loosely fasten the nylon stand-off nuts. Offer the circuit board to the acrylic sheet to make sure that you have the correct orientation (I've done this too many times to imagine that I'd get it oriented correctly the first time). If you've spun you board around twice and it still isn't fitting ... don't forget that you can also turn the acrylic sheet over and try again!

When my circuits are approaching final use or I'm actually going to do something with the circuit, I've made some acrylic enclosures by building sides (and tops) for the single plane acrylic mounting boards.

Of course, you may want to use another colour or opacity of acrylic sheet. Fortunately, it comes in so MANY different colours, opacity, texture, thickness ... the world is your shallow water marine bivalve.

If you look closely to the enclosure above, you will see that my early work in this area was ... well, to be blunt ... rubbish. Still, the enclosure does what I want it to do and my rework later is much improved.

The acrylic mounting board is very useful for mounting more than one circuit board. For instance, I have a mounting board that has 2 Arduino (UNO and Freetronics) an ATTiny84 and ATTiny85 prototyping board and a power supply. It makes a handy electronics bench tool, although, I prefer the single module style.

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