A few months ago we did a blog post about our variac. It was tripping the circuit breakers on our distribution board and we made some mods to the variac to reduce the inrush current. Our story generated a lot of interest and was picked up by Hackaday. We used a 2 terminal NTC inrush current limiter from Ametherm.
Following our story, the good folks at Ametherm and Rhopoint Components (our local distributor) were in touch with us. They gave us some great technical advice and did some calculations for us. They have a whole range of limiters and it turns out that we had actually chosen quite a good model for our application. They kindly sent us some samples.
There are many ways to soft start a load. We originally thought about adding a series power resistor and a shorting relay. We also had some suggestions around Triac and IGBT solutions. Each of these methods have their merits and can allow fine grained control of switch-on. Unfortunately there was very little room inside the variac case and we didn’t want some kind of external box. So we looked at these relatively simple 2 terminal limiters.
Carefully chosen, these components are an elegant solution. They can probably last the life of the application with no maintenance. Placed in series with the load, they have a relatively high resistance at room temperature which limits the initial inrush current. When current flows through them they self-heat and the resistance falls very quickly, so they have little effect on the normal operating current.
Well we’re at it again. Once a year we all have our birthday and TOG is no different. This month we have reached the ripe old age of 8 years. We’ll be celebrating in style on Saturday 28th January in Blackpitts. Last year we combined our January Open Social, birthday party and grand opening, into one monster bash. It didn’t disappoint. It was our biggest social event ever. The craic was so mighty, that we’ve decided to do it again this month for our 8th birthday party. So note that time and date….. Saturday 28th January from 7PM. There are strong rumours of cake, TOG beer and pizza.
Once upon a time, TV repair shops were everywhere. Now there are hardly any left. There are reasons for that, probably based on a mix of cost, reliability of electronics, and a throw-away culture. Even in the few TV repair shops that are left, would anyone actually take a scope, schematic and a soldering iron to a TV these days? Maybe they would just replace the circuit board or display.
Well the world has turned and another year has almost passed. What a year it has been for TOG. We started 2016 with our doors closed to the public. We had just made our big move from Chancery Lane. Blackpitts was a blank canvas for us. It was a completely open-plan space and we had to decide what to do with it. It wasn’t long before we had a proposed layout and we started building rooms. We built ourselves a fantastic common room, a classroom, a make-room to house our laser cutter and electronic stuff, and a general workshop. We decided that our traditional January birthday party and Open Social would be our grand re-opening to the public . We billed it as a monster bash, and it didn’t disappoint. It was our biggest social event ever. We invited just about everyone that we could think of, and most of them came.
Our regular Open Social evening for December, will take place on Saturday 17th December at 7PM.
By now, you’ll probably know that we hold a regular Open Social evening on a Saturday in the middle of each month. November will be no different. We’ll be doing it on Saturday 19th November. This month however, there’ll be a bit of a twist!