Author: gary

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Lathe Surgery….update

This is a tale of going to TOG to do one thing, but ending up doing something completely different. The intention was to write some code to talk to some electronic hardware. Actuality was taking the lathe apart. You can’t get more different than that.

One of our members reported that the lathe was unusually noisy and also a faint burning smell. We thought that it may be splashes of oil burning on the hot halogen lamp, but soon ruled that out. We disconnected the drive belts from the motor. The motor turns freely by hand, but seems to be hesitant in starting. It’s also drawing way too much current. Needs a bit more troubleshooting. Hopefully just a bad capacitor or something else simple.

 

Update…. so its bad news. One of the motor windings is burnt out. But it’s no big deal really. We’re sourcing a new motor. They’re not that expensive. A nice project will be to add some overcurrent and thermal monitoring to it, as well as an RPM readout. Sounds like a job for an Arduino!

 

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TOG April Open Social

Hey All…… Sorry for the very short notice but…. this month’s Open Social evening takes place this evening, Saturday 15th April at 7PM.

If you’ve never been to our Social, you’ll find it a great alternative Saturday evening in town. Come in and look around. If you’ve never been in before, we’ll give you the grand tour of the space. Talk to members and visitors about projects or things you’d like to do. Ask about our our new brew room and photography darkroom that we’re getting ready to build. If you like what you see, ask about joining as a full member.

Hopefully there’ll be, caint, ceol agus craic as usual. The space stays open until the last member is left……usually the small hours of Sunday morning. The evening is free to attend for members and visitors alike. No need to book…. just turn up. You can drop in for 10 minutes, or stay the whole night. We have parking available. Bring beer, food, gadgets! Our doors are open from 7PM. Hope to see you there.

https://www.tog.ie/
https://lists.tog.ie/mailman/listinfo/tog
https://twitter.com/TOG_Dublin
https://www.facebook.com/togdublin

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More Ebike Fun

We’ve posted before about our tinkering around with Ebikes. One of our members had a faulty Ebike battery.  Opening it up, the battery management circuit was found to be toast. We sourced a new one online from China, fitted it, and the battery is back up and running. We are thinking of making some spare batteries from old laptop batteries. We’re also thinking of having a TOG loaner Ebike. If you have any old laptop batteries that you could donate to us, we’d be interested. If you’d like to take a look at our Ebike works, drop in to our regular Monday evening Electronics night.

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Pizza Oven Rev 3

Back in our Chancery Lane days we made a very successful pizza oven. It became a regular feature of our monthly Open Socials. In late 2015 we moved to our fantastic new space in Blackpitts. One thing we don’t have in Blackpitts is our own dedicated outside yard. We can do things outside, but it is a shared car park so we can’t leave things out there. This means that we’ve had to build our oven every time and take it down again, for special occasions like our annual birthday party or summer post-Dublin Maker BBQ.

So its been on the to-do list for some time, to make a portable version that we can wheel in and out as required. We started the process yesterday to build a molded dome from lightweight concrete. There are lots of plans on line for this using a gym ball as a former. We’ll be working on it over the next few weeks. Drop in and have a look.

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TOG February Open Social

This month’s Open Social evening takes place on Saturday 18th February at 7PM.

If you’ve never been to our Social, you’ll find it a great alternative Saturday evening in town. Come in and look around. If you’ve never been in before, we’ll give you the grand tour of the space. Talk to members and visitors about projects or things you’d like to do. Ask about our our new brew room and photography darkroom that we’re getting ready to build. If you like what you see, ask about joining as a full member.

Hopefully there’ll be, caint, ceol agus craic as usual. The space stays open until the last member is left……usually the small hours of Sunday morning. The evening is free to attend for members and visitors alike. No need to book…. just turn up. You can drop in for 10 minutes, or stay the whole night. We have parking available. Bring beer, food, gadgets! Our doors are open from 7PM. Hope to see you there.

https://www.tog.ie/
https://lists.tog.ie/mailman/listinfo/tog
https://twitter.com/TOG_Dublin
https://www.facebook.com/togdublin

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Fixing the Variac……..Part 2

limiter

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.

We have now done a rev 2 of our mod. This time selecting the model MS32 5R020 limiter. It has a lower cold resistance of 5 ohms which should keep the operating temperature down a bit. Originally, we connected the limiter using PVC insulated wire, solder and heatshrink. Given the relatively high temperatures, we have replaced this with tubular glass fibre insulation and ceramic connectors. We should have no temperature worries now.
One other gotcha we found, is that our distribution board circuit breakers are actually B-curve and not C-curve as we earlier thought. That makes them even more sensitive to surges. When we did our original mod, we didn’t do a full load test. We did a quick run with our heatgun (about 9 amps). This time we did a full load test. At 12A of output current and an ambient temp of 20 deg c. The body of the limiter measured 200 deg C, which is hot, but below the 225 deg C max rating of the device. This was quite an extreme test, but we’ll continue to monitor and do some tweaks if possible.
If you’d like to take a look at our variac, or do something else with electronics, our regular Electronics, Microcontroller and IOT evening takes place every 2nd Monday. Check out the events section of our website for details.