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Posts Tagged “electronics”

Went to the London Festival Of Railway Modeling today, mainly to look at various DCC products, and possibly buy a booster to speed up development of my controller.

On the DCC front, lets just say I wasn’t impressed. The items on sale were under featured, many had user interfaces much like an early 80s pocket calculator, not good at all. There was a couple that had nice interfaces but they were up around the £400 mark, ouch.

On to the booster, the cheapest was around £150 for a 4A unit, way too much, there was an 8A for £250 too. Considering the modern N gauge locos draw somewhere around 50mA-100mA theres no way i was pay that much, just to help development.

In the end I spotted a Hornby Select for £60 which has a built in booster capable or just under 1A, with a bit of modding (15v -> 12v and bring out the logic level DCC rails) it’s woking a treat! yay.

I’ll also be adding a video of some of the layouts to this post at some point.

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Trying to figure out what to do with the Value Line chips I decided to make a Persistence Of Vision text display, fitting in all the best bits of the ascii table.

The font in 5×7 pixels making the it 470 bytes including a smiley.

Ideally it wants a way of programming it without rewriting the whole program, perhaps a low speed soft serial on one of the Port2 pins, not sure yet.

The source file can be found here main.c

or here in this text box:

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Having a strip of breadboard attached to the Launchpad is quite handy, the only minor problem is the pin labels, or lack of, since they’re printed on the PCB.

So I quickly made up these labels to stick on female header, they include extra GND and VCC labels.

If you have trouble with the GIF I’ve also made a PDF, which can be downloaded from this link
http://www.beigematchbox.co.uk/blog/wp-content/uploads/2010/09/ti_launchpad_header_labels.pdf

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Just a quick video demonstrating the skeleton program for controlling lights on an RC truck (Axial Honcho) from the transmitter with only a 2 position switch (Ch3) to control normal/mode selection, and the steering to choose the mode.

The box can currently handle 8 LED channels, such as brake/tail, headlight, left indicators etc.
It gets it’s channel information from the 3 servo connectors on the receiver.

I’m also considering ways to monitor the motor speed, with that and the throttle position it will be possible to work out when your driving in reverse, so turning on a reversing light.

And yes, thats an Arduino, a Pro mini at 8MHz on 3.3v.

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Well, in the case of the breadboard, RGY??…
Just have to use your imagination

Anyway, I’ve been wanting to make an audio visualiser for a while, looked at many ways of going about driving lots of LEDs with brightness control almost all using various chips to generate a separate PWM for each LED, to me this sounds all to easy… So I set about doing it with just an Arduino with an ATMEGA168.

The layout is basically the same as a normal common anode LED matrix, except the anodes are PWN driven.

The software is all done through the main loop, no interrupts. This makes things a little more interesting, having to keep the loop nice and short, basically as long as it’s under around 800us it wont interfere with running the LEDs.

Plan is to connect up a pair of these giving 10 leds per audio channel using serial to keep things in sync, such as the mode, buffer size etc.

Once I can find some nice small 4 pin polarised connectors for the LEDs I can hook them up, which should show off the effect nicely.

Oh and the matrix scans at 100Hz, which beats a little with my 50Hz camera, to the human eye the effect is smooth.

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The first VCF in the UK, lots of old kit to play with, and lots of friendly geeks! A good day out.

And a quick video, no plot, just some random clips.

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Something I’ve had in mind for a while is a nice simple iPhone app that’ll send data to an arduino over a network. I seem to remember some people using an app designed fir controlling some audio software i think, but setting it up seemed like a tricky process.

This afternoon I put a little app together that sends a single byte on a button press, and 3 bytes when the slider moves $, slider, value, the idea being you set the IP and port of your Arduino (with ethernet board of course), the iphone connects and off you go.

No idea if such a thing would be accepted on the app store, but I think it may be useful enough to polish add some connection monitoring and give it a shot.

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This article includes details on making a simple volume control box for when you want to hook up an MP3 player or similar source to an car amplifier without a head unit.

Basically, you want a way of limiting the amount of signal getting to the amp, you could use the built in volume on a MP3 player, but this will be a bit course and in general isn’t great for adjusting while driving.

So, you need to add a pot to each channel, the second picture shows quite nicely a dual gang pot, which is just 2 pots with a shared knob.

The second part is controlling the power for the amp, car amps have a remote power line, taking it high (to 12v) will turn the amp on, and making it open circuit will shut it down. All you need to do is simply put a switch between the blue wire on an ISO connector and 12v, this can be ignition switch or constant. You can also easily fit a LED, just put it between the remote side of the switch and ground, with a 4k7 resistor.

One important thing to note: Do not connect chassis ground to audio ground, as this will generate some pretty amazing hum!

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I decided it’s time to get a HD camera!

Most of my videos end up online, so the biggest requirement was for the videos to look good at 720P, and I think this camera does the job nicely.

The video has a look at the camera itself, as well as some unedited footage.


Please excuse the typo in the URL, oops…

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I’ve finally got around to making another intervalometer, this time better, faster, stronger… Detailed info will be available once I’m happy with the software.

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