Project – Page 8 – Tog Hackerspace

30/05/201624/07/2016

Project: Fun with a GPS Tracker

Checkout some pics here of a GPS tracker we got to play with. This is nominally a vehicle tracker, but it could also be considered for other tracking applications. The unit is small and is powered from 12V. It draws up to 100mA. A regular SIM card is inserted. The unit has an external GPS antenna and a mobile phone antenna. It has a few other inputs and outputs too.

When power is applied, the unit is ready after about a 1 minute startup. When the number is called, the unit replies with a text message containing latitude and longitude as well as a Google maps link. Opening the link takes you to the location. If you would like to tinker with electronics or stuff like this, drop in to our regular Electronics, Microcontroller, IOT and CAD Evening every other Monday. Check the events section of our website for details.

17/05/201624/07/2016

Line Following Robots

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We recently ran a Electronic “Build-It” Workshop. We have twelve build a line following robot. The little robot was an all analog device, not an arduino insight. Check out the photos from the workshop in our gallery and the video below of them inaction.

Join our mailing list to keep upto date with our workshops over the summer.

15/05/201624/07/2016

Featured on Hackaday : Taming A Variac With A Thermistor

We are delighted to have one of our member’s projects featured on Hackaday,

TAMING A VARIAC WITH A THERMISTOR

The folks at TOG, Dublin Hackerspace, have a large variac. A variac is a useful device for testing some fault conditions with AC mains powered equipment, it allows an operator to dial in any AC output voltage between zero, and in the case of TOG’s variac, 250V.

Their problem was with such a magnificent device capable of handling nearly 3KW, it presented an inductive load with a huge inrush current at power-on that would always take out the circuit breakers. Breakers come with different surge current handling capabilities, evidently their building is fitted with the domestic rather than the industrial variants.

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Read the full story over on their website. http://hackaday.com/2016/05/15/taming-a-variac-with-a-thermistor/

This is not the first time we have been featured, the Twitter Knitter got the Hackaday treatment too. http://hackaday.com/2013/08/20/twitter-knitter-combines-40-year-old-hardware-with-modern-social-media/

11/05/201629/03/2017

Project – Green Screen in Tog

There is now a green screen on the wall in the back. Please feel free to use it.
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It’s basically some sheets of plastic, painted with matt green paint that was lying around in the space. It has been tested with a Samsung Galaxy Note 3 camera and iPhoto and it blends seamlessly. No shadows or marks blended into the final product.

To get the best results use a good quality digital camera that doesn’t bleed colours. Using an old JVC DV tape camera from 2004 which bled around the edges left a halo in the final product. A still camera with movie facility with automatic exposure settings totally messed up the green screen effect.
green1 green4

09/04/201611/05/2016

Fixing the Variac

variac

Actually there was nothing wrong with it. It didn’t really need “fixing”. A variac is a kind of variable AC transformer. They are very useful for testing AC loads because they can give a variable output voltage usually from 0 up to some value. This particular one can output from 0 to 250V and supply about 12A of current.

It is rated at 3kVA which is quite a bit. A big horse of a transformer like this has a big inrush current when it is plugged in. The surge is so great, that it was tripping the circuit breaker on our distribution board. The breakers on TOG’s board have C-curve trip characteristic, so they’re really not suited to this kind of load.

So something had to be done to limit the inrush current. We thought about a power resistor and a shorting relay, but in the end opted to try an NTC type surge limiter. This is a type of resistor where the resistance falls with temperature. At room temperature the resistance measured was about 12 ohms. The resistance falls rapidly as the temperature rises. Even so, the thing gets hot at heavy load. We used the 2kw heatgun as a heavy test load. We mounted the limiter high up inside the enclosure, in free air. Plenty of insulation and some cable ties to secure it. Tested it and no tripping now. A bit more testing is required however. particularly at higher currents. Need to do some I²R calculations and temperature measurements. Pics here.