Wednesday, December 19, 2012

Solid State Relay Switched Mains Rig


For a number of my upcoming projects I need a rig to test the functionality of a solid state relay that would be driven by a microcontroller and switch the mains for other devices. Having done projects with similar requirements in the past I remembered how much pain it was to test the solid state relay (SSR) with naked mains cables running around, etc. This time I decided to create a marginally more sophisticated setup that would allow a quick, easy and safe way to do this. Also, now that I have made this once, I can reuse this rig in any future project with zero effort. Making this took about a day's work - most of the time was spent on finding materials that suited my needs.

This mains output is switched by a solid state relay, baby! :)

Monday, December 3, 2012

Programmable Timer Switch

Finished unit mounted on the wall, in use.


This project, like others before, has started out of need: our 30+ year old mechanical timer for the central heater of the house has finally given it up. It would have been faster and cheaper to get a replacement from the local hardware store, but I decided to learn something new and I set out to create a digital version of it.

I wanted to create something simple, something that anybody can use without any experience in electronics - i.e. not a geeky device that could only be used by me, but something that anyone living in the building could set up properly, given a User's manual.

I did a quick research asking people in the building (mostly relatives) about what functions they would like to see in the new timer. As much as I wanted to cram as many features in the device as I possibly could I had to leave most of my ideas for another project - the consensus was to be able to set up periods of time (from now on: time slots) within a day when the heating is on. Period.

However, with some modifications in the firmware new features, like time slots set up for any day of the week or month, could be easily added.

With minor modifications of the hardware this could be extended to several channels, i.e. more than one "item" could be programmed to be switched on/off in a given time slot.

This timer is currently used as a timer switch for the central heating of the house, but it can switch pretty much anything you attach to it. I will still refer to the output as heater for the rest of the article.

As usual, this project is available as kits or fully built units - for details, please drop me a line.

Saturday, October 20, 2012

Relative Clock/Timer/Alarm


Towards the end of the '80s, when I started out in electronics, one day I decided to make a special alarm clock: one, that, when the time comes, switches on some device in my room - be it a radio, TV or anything else. At the time microcontrollers were not easy to find and I didn't even know how to deal with them anyway, and so I decided to make this circuit out of TTL chips (74xx series). To make it easier (and also to raise its geek factor quite a bit :-) ) I decided that the clock should not show the actual time and the time the alarm is set to, but to show the remaining time to the alarm event. Since I needed the alarm for the same time every day (for school), I quickly learnt to convert it to actual time.
The fully assembled unit - missing some decorative items after having been kicked around for the last 20 years...

Monday, October 1, 2012

TV Auto-off from the '80s


In the eighties most TV sets did not have the sleep function that is standard on today's TVs. My grandfather was known to fall asleep about 5 minutes into watching any program on TV in the evening. Then, the TV would go on all night long. Those TVs in the eighties consumed a lot of power, so one day I decided to make a small device that would automatically switch off the TV when he falls asleep. Also, this device had to be very simple to operate so that grandpa wouldn't have to attend a course just to switch his TV on and off...

Friday, July 6, 2012

Washing Machine Monitor


About a year ago we bought a new washing machine which seems to work nice, but it lacks a very important feature: it doesn't notify me when the washing is done. I usually start a new load in the morning and, even though the programs usually finish in about an hour, I tend to forget it and hang the cloths only in the evening.

The finished board - just add a washing machine and it's ready to roll! :)

After this happened a few times, I decided that as soon as the warranty period is over I would install a small circuit inside the washing machine and let it beep once the program is finished. (The circuit would be very simple as I don't have to dig deeply in the private parts of the washing machine - I noticed that when a washing program is over all three status LEDs on it blink at the same time.)

However, as time has passed, I forgot the wet clothes in the machine for longer and longer periods and it became clear I needed a solution for this as soon as possible.

I had the following criteria for any solution to be acceptable:
  • Since there is no power outlet in our bathroom (apparently, when our house was built installing power sockets in a bathroom was illegal or at least frowned upon...) it must be operated without a separate power inlet.
  • It should not void warranty of the washing machine (for obvious reasons...)
  • It should be very simple, easy to use, preferably no user interface on it at all. It should do only one thing, but it should do it well.
  • It should be cheap, easy to make using commonly available parts.
  • +1: it should be compatible with not only our current washing machine but with any other as well.
Probably, a simple timer would suffice (although different programs take different amount of time to finish), but I wanted to make something special (or geeky, one might say...) as well.

Friday, June 1, 2012

IR remote control experiments


I have a few projects in mind for the near future which all have one thing in common – they all require remote controls to be operated. So I decided to experiment with remote controls a bit.

A small selection of my huge pile of never or a very long time ago used remote controls that are waiting to be repurposed.

Wednesday, May 23, 2012

Laptop touchpad/mouse pad salvaging

I was recently given a very old, dead laptop. I soon took it apart to see what parts I could salvage, what parts I could reuse in my projects.

Among the numerous parts there was one that I was interested the most: the mouse pad or touchpad. I was wondering how it is interfaced with the motherboard and if there is a way to use it on its own, like an ordinary PS/2 mouse.
This is the salvaged touchpad, back side. The other side is the actual pad that one touches.

Saturday, April 21, 2012

PIC based 3-axis accelerometer


At the time of writing this article I cannot really recall why I started out on this project in the first place. Maybe, because some time ago I was experimenting with the built-in analogue-digital converters of some PIC micros and was thinking that they could be used easily to interface the analogue output of an accelerometer… Maybe I saw something similar on a web site and thought I could make a better one… I don’t know. What I do know is that I like projects that involve LEDs (especially blue ones, preferably flashing most of the time :) ), interfacing with real world, and projects that teach me something new. So… one day I decided to make a 3 axis accelerometer – to see if I can make it – that could be used (as is or with slight modifications) in real life applications. I tried it in a car - it works great there, but at the moment I just have it sitting on my desk to entertain visitors.
The assembled 3-axis accelerometer

Saturday, March 10, 2012

ATX Bench Power Supply v2.0


I have been quite satisfied with the desktop power supply I made from an old PC power supply. My only problem with is that it takes up a lot of space on my desk. I have been long thinking how I could reduce its size and finally I realized that I don’t need an extra box around the power supply, I can mount the connectors on its original enclosure.

The finished item

Monday, February 13, 2012

Lil Bang (Sound Trigger for Cameras)


Now that I can take pictures of lightning I decided that I also want to be able to trigger my camera with sound. The design I came up with has the following features:
  • Controlled by a PIC micro (PIC16F886).
  • Adjustable sensitivity
  • Adjustable delay – i.e. the user can set how many milliseconds after the sound event the picture should be taken. (My uncle says it would be a lot better if there was a setting to define how much BEFORE the event it should trigger the camera – but that’s another project – for my Nobel prize later this year…J)
  • Operated from battery and/or external power brick.
  • Completely decoupled from the camera by opto couplers, so that no harm can be caused by the circuit to the camera.
  • Can be used with any camera that has a remote control input (direct, IR or otherwise).
  • Can also be used to trigger any other electronic device, e.g. flash

Meet Lil Bang - little bro of the Big Bang :)

Thursday, January 26, 2012

Fixing a Worn out Remote Control (XBOX, Playstation, Wii, TV, etc.)


The method described below is valid for any remote control that uses conductive rubber pads for buttons. I have successfully used the same method on TV/VCR/Home theater/AC remotes and game consoles. Some time ago I decided that the next time I do it I would document it here.

Recently, I ordered an extra controller for my XBOX 360 so that when my nephews and nieces come over they can play at the same time. The controller was advertised as a brand new, original controller from Microsoft. Well, it turned out it was an original, but far from being brand new. It must have been used extensively because all the buttons had to be pressed very-very hard to register. This is caused by the rubber conductive tips of the inside of the buttons wearing out after a lot of use. (For comparison, the controller that my XBOX 360 came with is still in top condition even though I have been playing with it for years.) Since it’s difficult and expensive to negotiate a return and replacement of product from overseas, I decided to fix it on my own. I have done similar fixes in the past with some remote controllers in the past.

Those black "dots" (11 total) are the ones that had to be fixed.