Time is running out

Posted on August 31, 2014


Njay: Hi dude. I’ve got some bad news about our little project. I’ve gotten the bridges to work with current limitation, but they don’t read out the actual current for you, and they warm up too much for my taste. I’m going to give them another try, but then I have to give up. Like I told you before, I’ve got some serious stuff to deliver in September and I can’t spend much time on this.

Vnevoa: What happened?

Njay: Well, the current reading is nearly impossible to do because the micro-controller doesn’t have enough free cycles to read out the ADC. At least nowhere near the 20 or 10 times per second you wanted. I had to implement the PWM control via software because of changes to the way I am switching the MOSFETs on and off, to save a lot of power and thermal shock by actively using the transistors for free-wheeling currents instead of their embedded diodes. But this ate up most of the available CPU, so now I’m not sure I can get current readings for you.  The blanket is too short, and I don’t have time to stretch it.

Vnevoa: Fine, no problem, current readouts are just a “nice to have” at this point. Forget it.

Njay:Yeah, but I also burned the whole thing during a test…. a damn short-circuit burned the mosfet, the driver transistors, and my I²C control console! I can rebuild them in time, but it’s going to be close.

When a chip releases its magic smoke, it is no longer able to perform its magic.

When a chip releases its magic smoke, it is no longer able to perform its magic. Copyright Ohmart.org.

Vnevoa: …

Njay: Well. Here’s what I’m going to do: I’m going to change the heat sinks on the bridges for better and larger ones; If I can’t finish that, I’ll pass it along to you.

Vnevoa: Cool. I’ll be waiting. Did you receive the I²C insulation chips yet?

Njay: Nope. The guy who made the order was also surprised, it looks like the online shop is mucking up that order continuously. First it got delayed because they were out of stock, now they didn’t ship it because they forgot to charge VAT… but also didn’t remember to say anything to him. Really sweet. 😦 Anyway… We’re running out of time. We’ve got 1 and a half weeks before the Maker Faire registration closes.

Vnevoa: Yep. Ok. Be cool, dude… relax. Do what you can, no more than that. 🙂

Njay: Yeah, well… We can get back on the project after the Maker Faire, but right now I got to fulfil my promises on a paying project. I really wanted to be at the Faire but responsibility comes first.

Vnevoa: Sure, I know that. No worries.

(to be continued…)Lisbon_MMF_logos_Banner_big