Paul & Sabrina's cheap DIY 144v motor controller

[MPaulHolmes]

That's right Alvin, make sure B- is furthest away from the big black capacitors, B+ is closest to the capacitors, and M- is in the middle.

Nevyn:
For the current sensor board, the MLCC capacitors (itsy bitsy) just have to be greater than 5v. Well, greater than 10v to be safe. 16v or 25v or 50v or 100v is pretty common.

[wakinyantanka]

Originally Posted by Nevyn

I have one problem. What voltage caps do I need to get? I feel like such a dunderhead.

What's the best way to solder those surface mount parts?

[MPaulHolmes]

I soooo own that! Get some rosin flux (not just any old flux). Let's start with a capacitor. brush a little on the 2 pads. take a toothpick and slide the capacitor so it sits on the 2 pads. put a little solder on your soldering iron. hold the capacitor down with the toothpick, right in the middle of capacitor. touch the soldered soldering iron to one of the pads/end of cap. take soldering iron away. Hopefully, you have a nice solder joint! Then get a bit more solder on the iron, and touch the other end of the cap. You won't need the toothpick then, because it's being held down nice from the first solder joint.

Hey, isn't that funny, that solder makes bad fumes, and it's called a solder joint, and it's illegal in california. haha.

For the little surface mount chip, I put rosin flux on all 8 tiny pads, and push the little chip on the pads. heck you can even put a tiny bit of flux on the legs after you move the chip on the pads. Then, put a little bit of solder on the iron, hold down the chip with the toothpick, and then touch one of the corner legs/pad with the iron. hopefully it's a pretty skinny tip! haha. make sure all the legs are on their respective pad before doing any others! after doing 2 legs, there's no easy way of going back! duh duh duhhhhhhhhh.

[pnikolaj]

Alvin got it. The bus bars were reversed. The smoke is not shown in the video, that occurred previously and was not captured on tape. I then went back to the instructions and realized I marked the bars based on the instructions on page 32 ("Also, make sure B- is attached to the bottom, and B+ is attached to the top.") after I had assembled the whole board. I was not paying close attention that what was the bottom on page 32 is now the top and vice versa and therefore marked the bus-bars incorrectly. Might I recommend, when the instructions are revised, a note stating which bar is which on the last page for the less educated like myself.

[jackbauer]

Paul i got the boards today thanks. Question. Do we have software for this new board or does it run the same as the 2c? Now i gotta solder that smt current sensor. I hate smt parts. Bring back valves (tubes) i say

[MPaulHolmes]

I'm not a huge fan either. It's just that the dang current sensor doesn't come in through-hole. makes me mad. And the LEM that can measure thousands of amps is hundreds of dollars I believe.

There is different software. I have done some minor testing with it, but it will be a couple days before I can debug it because I left the stupid computer plug down in oregon and the laptop battery is dead.

[jackbauer]

Yeh no problem i just wanted to be sure before ordering parts. Think i'll use this board for my liquid cooled 1000amp monster

[DJBecker]

Originally Posted by jackbauer

Paul i got the boards today thanks. Question. Do we have software for this new board or does it run the same as the 2c? Now i gotta solder that smt current sensor. I hate smt parts. Bring back valves (tubes) i say

A bunch of interesting parts are available only in surface mount.

Small boards like this are way easier than you expect. The critical element is a solder mask layer on the PCB.
I've been amazed at how well it works.

I use solder paste (not "soldering paste" e.g. flux) and a hot air gun.
Specifically the inexpensive "Mechanics" brand bought from DealExtreme and a $10 hot air gun from Harbor Freight.

Dab a tiny amount of paste on each pad, place the part, wiggle a bit and remove it to make certain that the ink-like paste has spread evenly. Reversing the part helps even out the paste. Smearing outside the pads is no problem, it actually helps see melting progress later.

Once everything is placed, put the board on a level heatproof surface. With low air speed heat the board from far enough away that you don't blow the parts away. Nothing will happen for the first 30 seconds or so, then the solder will suddenly "flash". All of the paste smeared on the solder mask will just instantly disappear, sucked into the joints or left as almost invisible grains that dust away later. Keep heating for another 10 seconds or so. Now the hardest part: don't touch the board for five minutes. I've picked up boards after seemingly minutes (OK, maybe only 20 seconds) only to watch parts shift or slide off, molten solder trailing.

This doesn't work as well on bigger boards will different/bigger size parts. There you have to gently preheat everything to a controlled 100C or 125C, and be careful to use the hot air evenly during the re-flow stage. The preheat keeps the big parts from absorbing so much heat during reflow, and it needs to be gentle to drive off moisture so that you don't get micro steam explosions.

[DJBecker]

A related topic: I don't think the fumes from regular soldering are as harmful as you think. The annoying smoke is from the rosin flux. Somehow the convection air flow always puts it right into your eyes and nose. But as long as you are soldering with normal heat, it's almost all flux smoke and no vaporized lead.

The danger from lead comes later, when it corrodes into active compounds. And during scrapping. The widely publicized problem, which I suspect isn't quite as common as it's made out to be in the alarmist stories, is in metal recovery. Some small-scale operations in low income countries recover the metal by de-soldering the parts over an open flame. That vaporizes the corrosion compounds and even some of metallic lead. All with people leaning over the boards, pulling off the parts.

Bottom line: a soldering iron on a fresh board is mostly safe. Don't ever solder or desolder with an open flame, and take care when re-soldering a corroded connection.

[steiner]

Jack,

What are you using for a recirculation pump? Any idea what the flow rate is?

Thanks...
Rick