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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.

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OSM MapJam Saturday 23rd of April

OpenStreetMap (OSM) Ireland members will meet Saturday 23rd of April in Dublin and do OSM mappy stuff on laptops in TOG. Like an indoor mapping party / hack day / social meet up / barcamp.

What is OpenStreetMap?
OpenStreetMap is a world wide, open content map. It’s often referred to as the Wikipedia of maps in reference to the fact that it is open to be edited by anyone.

If you’d like to learn more about OpenStreetMap, come along! Want to start mapping your local area, and want help? Come along! Want to find out how to use the low level OpenStreetMap data? Come along! This event is open to all.
If you’re already an OSM mapper and would like come, but not sure what to do, don’t worry we have loads of townlands to map and plenty of people who will give you a hand learning the details.

In addition there will also be a meeting of the Irish Open Source Geospatial Foundation, their first in person meeting. OSGeo was created to support the collaborative development of open source geospatial software, and promote its widespread use.
Where and When?
Tog Dublin Hackerspace
Saturday 23rd of April 2-5pm
Open Street Map Ireland Website

Worldwide editable map

OSM Ireland email list

Open Source Geospatial Foundation

OS Geo Ireland email list

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TOG Brewday (Saturday 26th March 10.00am)

TOG members and Capital Brewers will brew in the new TOG HQ this coming Saturday. Hearty brews are on the menu, in both brewing with guidance and instructions from the experts, and tasting craft beer made earlier!

A very rough time-line of a brew day is as follows:

  • 10am – 12pm: Heating water, water treatment and mashing grain
  • 12pm – 2pm: Boiling & beer tasting from previous brews and visitors beers
  • 2pm – 4pm: Cooling and clean up

Every brew day is slightly different with a mix of brewers, recipes and techniques. This weekend Fergal will be brewing a session IPA, similar to the “Via Maris” beer from Galway bay brewery.

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Brewing equipment in TOG

Over the past few months we have been building up the core set of brewing equipment in TOG to reach our goal of getting a full set of brewing equipment in TOG. This would allow TOG members to brew themselves at the space and make your own beer, cider or wine whenever you like! All you need are the ingredients. This event that usually happens every second month so if you can’t make this brew day there will always be another opportunity.

Its always a fun and engaging day, the cost is free (donations are welcome) so come along, ask questions and even help with the brewing!

Capital brewers discussion is here, and pictures of our previous brew days can be found here.

Video from one of the brewdays last year in the old TOG space:

Edit, here are a few photos from the day:

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Bridge Building Results

We had out 4th annual bridge building sessions for engineers week last weekend. With 80 tickets sold we had a fun packed day.  The winner bridge held an impressive 28KG before breaking. They are pictured below.

 

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We had a great talk from Cahill Fergal, which lead to some many different bridge designs. Check out our gallery for all the snaps from the day. -> Gallery.

As with every year the best part of the day is the destruction. The scouts really got behind the sprint of the day.

Finally we would like to thank Engineers Ireland for the financial support to make this event possible and the volunteers from the Young Engineers Society