Add-on boards are working!

Posted on September 9, 2014

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NJay: I got them both to work! Whew!

Vnevoa: HOORAY FOR NJAAAAYYYY!! 😀 What now, do I get to play with them or you keep them a little more for testing with the bridges?

NJay: Take it easy, I need to test the whole thing together, the 2 bridges and the 2 add-ons controlled by the console. I need to see if there are any more surprises first. Besides, I still need to finish up the bridges themselves and you know I have my free time on high demand right now; one still hasn’t got the heat sinks properly assembled and the other I need to check the software is the latest version and has the proper Slave address. And. I’d also like to clean up the code a bit, review and optimize…

Vnevoa: Dude, forget it! We just need it running, yesterday. Don’t fiddle with the code unless you absolutely have to. Focus on getting it working, and that’s it. We’re not building a Nissan Leaf, it only has to take a few hours of riding.

NJay: Okay, okay. I’ll probably be able to give you all the boards in 2 or 3 days…

Vnevoa: I’d be happy to take over the testing, but you’ve got all the big boy tools for doing it. 🙂

NJay: Yeah, I’ve got the whole environment set up, it’ll be quicker that way. You’ll have your share of work with the mechanical side… I’m worried that the MOSFET pins will break, you really need to think over the attachments of the power bridges to the trike, and the heat sinks really need to be attached to each other to prevent movement. Did you know that the pins of the TO-220 package can break by fatigue just from the vibration, if you just leave the component soldered but not screwed? Now imagine that it has a large heavy heat sink attached without any other support…

Vnevoa: Each bridge will be a solid part, with the 2 heat sinks attached to a base plate and to each other through your add-on board and a few metal strips. I’m thinking of using those magnetic locks that you see on cupboard doors. A couple of them per bridge, to hold down the base plate where the bridge heat sinks actually attach. That way we can remove the bridges fast and simple in case we need to mess with them.

NJay: Hmmm… that’s a cool idea, but I’d be happier if you’d also put up some hard stops around the plate to secure it and prevent sliding.

Vnevoa: Done. 🙂 So, what was the problem with the add-ons?

Njay: Two problems actually: I had switched the SDA/SCL (Data/Clock) lines between Master and Slave (the chip is agnostic about that, but we need to be consistent in its use of course) and also, I fried the first chip. So, good thing I bought 4 of them. 🙂 They’re expensive, but I’ve got both boards working now. You’ll need to attach the temperature sensing diodes on the heat sinks, as near as possible to the MOSFETs. My initial design of the add-on boards had them built-in because I expected the old kind of heat sink, not this larger one; now you’ll have to tinker with it to get it right.

Vnevoa: My friend, tinker is what I do. Call me Tinker Bell! 😀

(to be continued…)Lisbon_MMF_logos_Banner_big

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