Wireless Launch Control

So this turned out to be a little more bother than expected. Starts out easy, some wires and R/C connectors. Goes together easily enough. But then it doesn't work. Doh!

Bang my head on the workbench for about a day, and then hit the web. Not much info on troubleshooting LiPo protection ICs. But as always nuggets can be found. Turns out you have to reset the circuit with an external charger after assembly before it will output a voltage. Then it works great.

Now I realize I can build my own field box battery packs, with charge/discharge protection and even balancing circuits, for a lot less than using R/C batteries, even as cheap as they are. Mainly because the individual LiPo cells can be had pretty cheap, and don't have to mess with those slightly expensive R/C connectors. But still not as cheap as a SLA or lawn tractor battery. But those guys aren't going to fit inside the field box either.

I didn't have any heatshrink tubing big enough to cover the circuit and wiring after I assembled it. So that will come later. And I need to get a different LiPo charger. The fancy one I have is for R/C packs and it doesn't like the 'protected' pack all that much. No big deal.

Enjoy the pix!!

Just to wrap this up. Some 3/4" heatshrink over the circuit

I was finally able to verify that the over discharge protection works properly. Took about 2 days with the field box turned on to run down the battery though. But the protection circuit did cut off the load at about 10.6v which is near perfect. Meanwhile also built a second module for the other 4S field box. The rest have 3S batteries or no internal battery

I've been puzzling over and solving a new problem, which was that no matter what I did, I couldn't charge the battery through the protection circuit. #$&*@#!

After a new second charger didn't work either I realized it was the protection circuit itself. The circuit can work with 3 cell or 4 cell packs, and it turns out that is configured via various components on the board. Just figuring out that fact took quite a lot of research. I had no datasheet on the circuit, other than how to connect it to a battery. Spent a lot of time searching for a datasheet. Cheap, high quality made in China circuit, but no datasheet or manual. Frustrating.

Via indirect reference I was able to find a datasheet for the Sieko analog controller chip in the circuit. So I was able to finally sort out what some of the missing components were for, and which existing components needed to be moved or removed to reconfigure for 4 cells. I destroyed a few chips testing but that also left me with some components to cannibalize for converting the other circuits. Another challenge was these various resistors and capacitors are literally flea sized. Each is about six 100ths of an inch long. So desoldering and soldering these took a little practice.

The good news is the reconfigured modules work great. And since the problem was never the charger I can use either the smart charger and charge at a full 1C rate, or the smaller charger at about a 1500ma rate. Either charger will keep to the LiPo profile and cut off current and voltage appropriately, plus the protection circuit makes double sure no individual cell gets over charged, which could lead to a fire. Coolness!

I also found some eBay sources for cheap bulk EC3 connectors and also those JST connectors for the balance leads. Real cheap and free shipping from Hong Kong!

Any news or progress?

cwbullet said:

Any news or progress?

Click to expand...

Not so much. I've been taking an extended break from it. But I do eyeball the pile of unfinished boards on my workbench from time to time and I will finish those up someday. And when I have some time I want to rework some of the software to make it work a little better. The communications should be better than it is. But despite some small issues the systems continue to work great. I recently bought a few raspberry pi single board Linux computers. To that I purchased and added a small interface board with a zigbee connector footprint. It will be fun to set up a fully interactive monitor program for the whole wireless setup.

I've decided to make this an open source project. Yep, a little late for that... But at least the information and knowledge will be out there for anyone who wishes to do something similar or take it further. Hopefully some will. It will take a little bit of time, and look for updates here. I'm still learning about how the open source thing works.

Recently I have finished building all the pad end PCB controller boards I had in my inventory. Ten of them actually. The boards need to go into boxes that implement the actual field box. That's still pending.

I designed a slightly new field box top panel that incorporates all my recent mods. And I've cut and milled and finished about 21 panels to retrofit and build new field boxes.

I had a major snafu with the firmware code a long while back which broke everything. Old wireless firmware images still worked but new ones did not. Couldn't figure it out at all which knocked me off the game for a good while.

Recently I got my hands on a slick new logic analyzer and I managed to figure out the problem after a couple of weeks. Literally changed one line of code at the master and the whole multi-node wireless system was up and running again.

Getting the project to open source will take a little bit of work. Could be a few weeks or more. So if you care, be patient. If not, so what?

Whether you care or not, any comments?

I might be interested in March. Too much on my plate right now.