Been a while since posting the forums. For the past two years I've been involved with ForZe Delft, a completely non-profit team of strictly students that have been building and racing Hydrogen Fuel Cell powered race cars for the last 6 years. We're currently working on the 6th car, that will use a 100kW fuel cell system, 200kW peak motor power, and weigh in at about 800kgs. Our previous cars were a lot smaller so it has ben quite the challenge! If you want to read some more there's some more info on the website http://http://www.forze-delft.nl/. Also, I'll be happy to answer any questions about the project.
As nearly all systems are self built, the Buspirate in particular has been a huge help on several occasions. My own BusPirate has been 'confiscated' by the team so I'll be in the market for a new one soon ;)
Anyway we have a bit of a problem on our hands at the moment. To deal with the slow response of the fuel cell, we use a supercapacitor accumulator (160x 2300F, about 600V) which has to be monitored. The monitoring circuitry has been based on the LTC6804 IC. Sadly there seem to be some problems with this IC running on higher temperatures (not a problem for us) so it has been discontinued by LT. Waiting on the new revision (~July) is not really an option. Now we happen to be a little low on stock with this IC and it's sold out at all normal outlets. I did find a couple of ads on TaoBao/Tmall, but not sure if that's really trustworthy. Does anyone here have any experience with this sort of thing? Or perhaps a different way to acquire said IC's?
[attachment=1] The PCB sitting on top of an SSR. It's nice and small, I'll cut up a power cable and put the SSR in there. I intend to make as little mods to the oven as possible, just a hole for the thermocouple.
Still waiting for PIC MCU, but did solder up the thermocouple part. It's a max6675 so used the BP to verify operation. Temps were looking fine so that's positive. Ill see if i can run a ramping test tomorrow to see if i need to decrease the volume or something. [attachment=0]
[quote author="SadE"]Nice Rubu !! :) You're lucky , my own order has been cancelled , I have to find another one :-/ You're right the most important thing is the monitored ramp test . What is the volume of your oven ?[/quote]
http://http://www.amazon.de/HLO-3322-Glas-1300-Watt/dp/B002UXQJZA That's the one, 1300W, 12 Liters. Pretty big, so who knows. I'm afraid it won't be fast enough. Already looked into decreasing the volume by filling up the bottom with something, not sure if that would make it better though. Ah well.
I bought an oven exactly like that locally (second hand) for 13 euros. Already have a controller PCB fabricated and all the parts except the PIC lying around. Not sure what to do with the fan yet. Haven't done any (monitored) ramping tests to see how fast it can ramp though. I think it's 1200W so we'll see how it goes. I'll probably get on it this week and I'll report progress in here.
Specs of the controller: -PIC 16F690 -K-type thermocouple -FT232R for USB communication -Powered over USB -SSR for switching the oven on and off
Did some prelim tests without a controller and that went fine. No QFN of big QFP's just some resistors, regulators. The fan didn't prove to be a big problem, but like I said, only minor tests.
I'll snap some pics of the PCB, SSR and oven when I get home later tonight.
Not sure about this, but I don't think a master will (always) ACK when adressed, and I'm pretty sure that's how the scanner works (right) Anyone can confirm?
I just received PCB's for something similar. Difference is that it doesn't have an LCD, but just USB for output. I can dig up the schematics soon, don't have them right here at the moment. Probably by monday.
It has an PIC18F690, FT232 for USB communication, and a MAX6675 for reading the thermocouple. Terminal connectors for Power (selectable with a jumper to be USB or Ext 5V supply), for the Thermocouple, and for an SSR (from ebay, ~4 usd). PCB measures about 4x4cm.
The firmware is as of yet non-existent. haven't started on it yet, but I have some knowledge of (PID) control so shouldn't be too hard. I'll have a look if the MCU has enough pins (and memory) left to drive a HD44780 LCD, because if it does that can easily be added.
Don't have a case, I was going to use double sided tape to attach the PCB to the SSR.
As for easy connection I was just going to strip a Euro-Cable, and attach that to the oven whenever I want to reflow something. As I'm not sure if the oven can ramp fast enough I wanted as little mods to the oven as possible. I'll probably need to drill a hole somewhere for the thermocouple, but that's ok.
The creator of the bitlair ones posted on a forum I frequent about those PCBs, it is indeed a LED controller. I'm sure you'll get his contact details from bitlair admin or something, but if not let me know and I can pull his e-mail from his profile or PM or something.
So did you document the PCB's you opened up or is someone else scratching his head about pondering about your board as we speak? ;)
Really nice job, I've done QFN16 without exposed pad with just an iron before, but never BGA. Starting to really consider getting a hot air tool, how are you liking the Atten 858D? Looks like a nice hot air tool that doesn't break the bank.
We have a 15kW programmable load at a project I work on. We also have some spare 2.7v 2600F Ultracapacitors. We've had the idea to push one of those to the limit, but haven't done it yet. We better be careful too because from where I stand that would qualify as "Dangerous" ;)
I thought about opening up my last PCB from iTead, but didn't have sufficient documentation so I decided not to. Next time I will i will at least put the part names (and values where there's room) in the silkscreen. If everyone would do it like that only the firmware would be a problem.
Lookin' good, gotta love your own birthday presents.
I've seen those weird angled traces before, always wondered why you would do that, seems to me it would be more trouble getting them like this than the 'normal' way, any idea? is it really that tight down there?
