Project: Remoteli – Finished

It’s been a long project. I think this is due to a combination of factors – a large number of manufactured parts, fiddly soldering and software troubles. Certainly at times I have struggled to find time to work on it, worsened by spending the year studying in America rather than the UK. Getting back into the project after waiting two weeks for a board to arrive was a challenge I faced more than once.

Nonetheless, Remoteli is now complete! (At just 39x18x4mm ignoring nuts and bolts)

Continue reading “Project: Remoteli – Finished”

Project: Remoteli – Plastic Spacer

Remoteli’s construction will be a PCB (the one I already have with all of the buttons on it), a plastic layer which is 1.6mm thick, and another PCB on top to cover all of the electronics, except for the switch, IR receiver and transmitter, and the buttons.

Today I finally managed to hunt down a 3D printer in order to print out the plastic spacer. Here are my designs:

It turned out a friend of a friend had a 3D printer I could use.

Being a small model, it only took 12 minutes to print and it came out pretty well. Unfortunately the detail around the screw holes and the top of the circle didn’t print well, but it was good enough to work. I didn’t really expect it all of come out perfectly anyway.

Here it is:

spacer and board

I was impressed how well the battery fit into the spacer. Now I am just waiting for the second board to arrive from OSH Park.

Project: Remoteli – Circuit Board Second Version

After some preliminary testing of the first version of the circuit boards, I found that they were pretty horrible for developing on. The reason for this is the programming connections.

To program the microcontroller, I use an AVRISP MKII programmer. These programmers use an SPI protocol to talk to the chip, so it requires a VCC, GND, MOSI, MISO, SCK and RESET connections. In the initial version of the board I made these connections by soldering wires to pads on the board and then connecting crocodile clips to these wires.

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As you can see, this got a bit messy and the wires kept threatening to break off. In fact, I also, embarrassingly, forgot to leave a pad to connect to the RESET line and so I had to precariously solder this wire onto the board which kept breaking.

This wasn’t the way I wanted to continue with these boards, it was stressful and took too long to set up. So I redid the boards and had them made again. Luckily this only costs $5.50, but unfortunately it also takes about 12 days, so it isn’t something I want to keep doing, but I’ve definitely learnt a lesson.

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The new version of the boards includes 6 copper pads where I can connect crocodile clips directly. This allows me to entirely the remove the programmer when I want to and doesn’t have any of those difficult wires. It also has proper silkscreening, and I’ve managed to solder on the IR receiver!

I’ve tested it out and it works nicely. I’m very happy with it.

 

Project: Remoteli – IR Receiver

Today I wanted to test out the infrared receiver. This is the datasheet. It’s got an internal 38kHz frequency filter so that it specifically picks up signals from a tv remote.

I decided to test it before mounting it to the board by soldering wires to it and measuring the signals. But it’s only 3.95×3.95mm large! After a lot of messing around with a soldering iron, I eventually had this.

The small shiny bit of plastic is where the light enters the chip

The small shiny bit of plastic is where the light enters the chip

I connected up a 3.3V power supply and put my oscilloscope on the output. The output looked identical to the signals from the IR receiver in my Infra-red Repeater Mini-project, so it looks like it’ll be just fine for this project.

Project: Remoteli – Bottom board

For this project, I’ve decided to start using Altium’s Circuit Maker, rather than Eagle, to design my PCBs. The main reason for this is because Circuit Maker is very similar to Altium Designer which is a professional-level package (and the price reflects it) so it’d be useful to be able to use it. Circuit Maker also has a very nice 3D view mode:

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Project: Remoteli – Design

This remote needs to be small, and the components need to be even smaller. This means I’ll be using only 0603 passive components. The microcontroller I will be using is an Attiny1634.

I thought about a few uCs before I chose this one, but I settled on this for a number of reasons:

  • It comes in a tiny 4x4mm QFN package
  • It has 18 I/O lines which is enough for ~12 buttons, an infra-red LED and an infra-red receiver
  • It has 16K flash which means I have a lot of memory in which to store learned infra-red codes

In order to learn new codes the remote needs an infra-red receiver so it can copy codes from existing (larger) tv remotes. This was a harder design choice, but in the end I settled on this a TSOP572. This is one of the few infra-red receivers I could find that had a low enough profile (<1.6mm) to fit between the two circuitboards.

Project: Remoteli – Specification

I don’t really care that much if this is the smallest TV remote in the world or not, but I want it to be as small as is practical. I also want to design it so it could be mass-produced, if I ever wanted to. So here is my specification:

  • Keyring attachable
  • At least 10 buttons
  • Easily reprogrammable to work with almost any TV
  • At least ~1 year battery life
  • Run on a coin cell
  • Only a few mm thick
  • Only a few centimetres long and a couple wide

To make this as small as possible, I’m going to use entirely surface mount parts, which will be a challenge in and of itself. I’m also going to use a design idea I first saw on an episode of the Eevblog:

The idea is that the device is made of two circuit boards which sandwich the coin cell and components. This way, using a cr1616 battery and 0.8mm thick pcbs I can achieve an overall thickness of only 3.2mm!

For his uCalc, Dave Jones uses capacitive buttons, however because this remote will be very small I think that the buttons will be so tiny that you’ll have a hard time pressing just one if you can’t actually feel the buttons. That’s why I have decided to go for traditions push buttons in my design. This means the buttons will poke through the top circuit board.

New Project: Remoteli – The Worlds Smallest TV Remote

So this isn’t really a new project. I’ve actually been working on it for a couple of months on and off. In fact, I already did a post related to it. But I wasn’t really sure if it was going anywhere or whether to post it. Now it’s gotten to the point where I have ordered circuit boards online and begun soldering so I think it’s a legitimate project.

The reason this has taken me so long is that I have recently moved to the US to do an exchange year at MIT. That takes some getting used to, so finding the time to work on hardware projects has been a bit tricky, but now I think I’m good to get back into the usual rhythm of building stuff.

I’ll post more detail on the project soon, but for now, I have a new soldering iron! A Hakko FX-888D.

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Because I’m currently in the US, this model actually runs off of 110V as opposed to the 240V we have in the UK. Therefore I’ll have to modify it in order to use it when I return home. However, even with the cost of a new transformer, it will still come out significantly cheaper than buying it in the UK!