Heating Oil Level Gauge
April 28, 2013 — 22:26

It seems I can’t just leave the central heating alone. When we got the heating in (after 2 years of zero heating here, cooold) the tank was fitted with a wireless level monitor which measured the level of the tank using an ultrasonic sensor and sent the data back to a base station plugged into a wall socket using its combined battery pack/aerial. This worked fine for a couple of months until the battery pack went dead. A new battery pack worked for a couple of days and it never worked again – exactly the same as the unit fitted to my parents tank , an absolute waste of money. I switched to dipping a stick into the tank which proved far more reliable but slightly inconvenient over the last two years.

A few weeks back i was browsing ebay, as i do, and found some ultrasonic distance sensors for about €4 delivered. (I have no direct link as the auction has expired but searching for SR04 will bring up any amount of similar units.) I had no plan for them immediately but I bought some just to have anyway. It was only after they came that it struck me that a way of remotely monitoring the oil level would be  a nice project.

The units are very simple to use. There is 4 pins: 5v, GND, Trigger and Echo. By applying a 10uS pulse to the trigger pin you activate the sensor to take a distance reading. The sensor replies on the echo pin with a pulse that is as long as the time taken for the sound wave to travel to the distant object and return to the sensor. Knowing the speed of sound we can then calculate the distance.

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DIY Heating Timer v2.0
March 4, 2013 — 2:16

Following on from my previous post on my DIY timer I wanted to make something that I could mount to the wall and not have my wife be ashamed of it! In passing on one of the car forums I frequent I said that I could modify my original heating timer to be controlled by a google calendar for less than €100. As you know that timer died while experimenting so i was left having to make one from scratch if i was to come good on my claim. Thinking about it an arduino combined with an ethernet shield and touchscreen shield could come together to make a very nice controller with a tidy looking interface. The hardware for that should come in under €100. 20 each for the shields and arduino and a further 10 for a solid state relay. It was while browsing DX.com i came across this. A 4.3″ touchscreen android tablet for less than 35 euro delivered – mind blown, I knew what i had to do.

jxds18

 

Hardware wise I needed a way of allowing the tablet to turn on the relay. I couldn’t use bluetooth as the tablet didn’t have it and it would be too unreliable anyway. The next choice for getting an output would be the vibration motor but again, the tablet didn’t have one. All that i was left with was using the speaker output to trigger the heater. To do this i had the software (detailed later) output two tones. Depending on the frequency of this tone we would know if the heating should be on or off. The speaker output is passed into an op-amp used as a comparator to give a nice 5v square wave that is input into an Attiny85 via one of the Boards.ie keyrings/dev boards i had made up. The attiny measures the incoming pulse and decides whether to turn the output on or not. The solid state relay can be directly controlled with an attiny pin. Here you can see the hardware during the prototype stage.

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Work Placement Needed
February 4, 2013 — 12:11

Due to a mix up/mess up with my university I’m left to either find a work placement on short notice or try find some modules this semester which I should’ve started over two weeks ago – something I don’t want to do as not only does it mean missed class time, it means choosing modules I normally would not have chosen both this year and next.

Ideally I’d love to get in somewhere small where I can get stuck in, and I find myself drawn to learning PCB layout and design but I am open to anything relevant and interesting. I’m based in the east, so I would be looking for Dublin/Wicklow/Wexford/Carlow area. I’m a mature student with a wife and 3 year old so moving away for 6 months currently isn’t an option.

I have an engineering science degree in electronics and this placement is part of my electronic and computer engineering masters.

If  anyone knows of any companies willing to take on someone I’d love to hear about them. I can be emailed at blog@chet.ie

Thanks!

LED Light Ready For Hacking
January 18, 2013 — 20:35

I bought one of these in Argos to see if there was anything interesting that could be one with it. It turns out that the thing is ripe for hacking if you wanted.

argos

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Heating Timer Mods -> Homemade Timer
January 14, 2013 — 11:06

For years our heating timer was sitting on the wall being not particularly useful. It was so awkward to reprogram new times into it that it had come to a point where it had a basic program on it and was mostly manually controlled by switching it on for 1/2/3 hours at a time. Finally i had enough of it and with some spare time on my hands i set about adding some remote control functionality to it. The first plan was to gain control over the “+hrs” button we were used to using and then see what was possible. In preparation i ordered an arduino ethernet shield but i wasn’t sure what i was going to do with it.

A popular method of controlling a switch with a microcontroller is to replace it with a transistor. As i didn’t want to interfere with the normal operation of the switch i traced back the pads on the switch to two vias on the PCB which allowed me to solder some thin wires in to attach the transistor to. To test i brought out GND and the base wire and reassembled. Running some simple code to toggle the switch let me cycle through the times and turn it off as expected.

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Scraping HTML from Websites with PHP
January 13, 2013 — 21:06

Here’s a simple and useful PHP script that i’ve used a number of times to pull data from an external site to use elsewhere. I first used it with my Cartell.ie android app. To minimise data use on the phone the entered reg number is sent to one of my webservers which requests the cartell.ie site, submitting the given reg and returning just the vehicle information.

The phone requests server/file.php?registration=<reg number> Where the registration number is first read into the variable ‘reg’


$reg = $_REQUEST['registration'];

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SolarSwitch v1.0
December 24, 2012 — 22:27

 

My brother has a solar panel on the roof of his house which is used to charge a 12v battery which runs the equipment in his attic, the routers etc. There is a proper solar regulator/battery charger which keeps the battery topped up. The problem is that when the sun isn’t shining (which happens a lot here!) the battery drains and eventually the voltage drops. He had bought a switch mode power supply that would take over from the solar regulator but he wasn’t sure how to wire it up to work as he wanted, which was to have the power supply on only when it was need so there would be no power wasted.

This is what i came up with for him.

2012-07-18 19.51.40

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USB Boost Module Testing
October 3, 2012 — 23:49

As you may have seen from the RC car mods posts, i had to add a voltage boost module in to get it working. While it worked perfectly for that purpose i was skeptical of the claimed specifications – as you should be when buying cheap stuff from ebay.

Here is the details from the ebay auction:

  • Input voltage: DC 3-4.4V

  • Output voltage: DC 5.5V

  • Output current: 700mA (max)

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Porsche RC Car Mods Part Two
July 26, 2012 — 15:13

Following on from the first post where the voltage was dropping when the motors were under load causing the arduino to reset i tried a couple of things to get around the problem, first i added another cap across the arduino supply and then i added another battery in series (to give 6V total) but still the voltage was dropping too much.

As i knew running an arduino from 4.5V was on the low side i went looking for a dc-dc boost to up the voltage to something more useful. What i found was a module used for charging USB devices from voltages down as far as 3V. These are rated at 700mA so more than enough for what we’re running off them. The actual output voltage is 5.5V which is in the acceptable range for the arduino.

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Porsche RC Car Mods
July 12, 2012 — 1:46

With the Dublin Mini Maker Faire just around the corner i treated myself to a new toy to hack in its honour, yeah i know, any excuse. Everytime i look at my 1:18 scale delta integrale (a reminder of the one i used to own thats sorely missed!) i always think that it would make a great project to add working lights to it and have them controllable. Then i remember how much the model cost and i decide not to chop it up, not yet anyway. As i was browsing the argos site to look for anything interesting and cheap i came across this Porsche 911 GT3 RS which seemed like a nice buy.

 

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