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April 15, 2008
Software developer by trade, electrical/mechanical engineer/tinkerer by hobby.
Update: I’ll preface this with I am probably pushing the limits of this board to begin with, mentioned in another post below, ~100lb 24v system: - I gave it a run outside for a few 15-30 or so second cruises, shut it down, and checked to see how temp of FET’s was in case things were going to heat up quickly. They were barely warm to the touch, so the current handling seems to be great on this board. After a few cruises around the yard and everything was running smoothly, I thought I’d give the hill a run. I rolled down it, got to the bottom, and the board was toast. In my completely non-expert opinion, it seems to be the board maybe doesn’t handle reverse / ‘free wheeling’ current in the H-Bridge well, as it barely warmed up under high load, and performed great, but with motors spinning rolling down a hill with no throttle (or very little), the board gave out. It now just has a dimly lit fault led on one side, and doesn’t respond to RC input (or even do the three beeps at power up) . If OddBot or spartkfun has any input on if this board is resurrect-able, and/or if some external reverse protect diodes to supplement the body diodes of the FET’s might get a replacement board by, let me know. I’d be happy to work with either to try to get this up and running.
Just thought I’d add I had a similar case; just as a quick test I threw the TRex in R/C mode with wheels up on the bot, and all was fine. Gave it a run around the living room a bit, saw a small flash on the board (arc-like), and after that giving it any throttle would just reset the TRex and it wouldn’t drive the motors. Pulling motor connections prevented the reset upon applying throttle. After reading other reports of issues on here, before much troubleshooting I just tried bypassing the main power cut FET since I already had a high-current toggle switch for power anyway, and I’m back in business. - by the way, while testing I had the board in a plastic box, so my FET toasting was unrelated to any chassis screws, and seemed like more of a defect in design or production.
News - Enginursday: Yeah, I foun…
about a year ago
I was curious myself and poked around a bit - This looks awfully similar, might even be theirs: http://www.ebay.com/itm/331119044135
about a year ago
about a year ago
Thanks for the clarification! - So I’ve got a probably about 100+lb lawn mower based off of a power chair I’m looking to replace the controller on. Running at 24V and climbing some 45deg hills while mowing, I’m betting the motors are pulling well over the 9A each, possibly even over 9A on more ‘normal’ terrain still. It sounds as if this is well designed with the PTC’s being the weak link, If I found I was tripping them after a decent period of mowing time, if I was heat sinking the FET’s and maybe fan cooling, I’m thinking I’d be pretty safe replacing the PTC’s with something of higher value (possibly even just a non-PTC)?
- Thanks in advance for any input!
I just thought I’d double check I’m not mis-reading something, but it looks like in the user manual (page 13) this TRex is rated at only 9A constant per h-bridge/motor, and not ‘average currents of 18A per motor’ as stated in the description here?
News - New Product Friday: Big M…
about 2 years ago
- I’d second ditching the continue button. Sparkfun has one of the neatest, cleanest layouts of any site I frequent with great write ups; I’d definitely pass on the ‘continue reading’ button becoming a permanent feature though. Scrolling past an article is easy enough if for some reason I don’t want to read it, and something might catch my attention and I’d decide to look at it while scrolling past. My preference would be it takes effort to not read an article, not effort to read it. I can’t say I speak for the general public though, so just take it as my 2 cents. I’m sure I’ll survive if the button stays. :-)
News - Androids Love IOIOs!
about 3 years ago
Agreed… I’ve done an RN-42 to homebrew arduino before to get a project talking to an Android device, and I guess I’d just rather spend the extra $20 or so to have a slim and trim one board solution rather than spend the time wiring up an RN-42 and arduino (or Propbridge), and more time futzing with the config/code. Both valid options, although by the time you buy and config bluetooth to something else the elegance and simplicity of using this would be hard to beat I’d think.
No public wish lists :(
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