It’d probably end up being easier to just grab something like that Jaycar kit for speed control, and use a relay for forward/reverse. Any DPDT relay should do, just gotta make sure the motors aren’t running before switching.
Thats what we’ve done, relay H-bridge with that 20A jaycar kit. Blair is putting together the electronics now.
I need as much help as I can get over the next 2 days, I’ve got almost everything welded and now its just a matter of giving the parts a little grind in a few spots and putting everything together. The only thing I have still to make is the crank which i’m starting on now and should be done this evening.
If anyone has any time to spare at all, please come in and give me a hand.
I will be in after 6pm tonight for as long as I can manange
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Hey guys, a little late to the game here, Is it moving yet? I can help out tomorrow morning.
I was thinking of making a Power Mosfet H-Bridge for the robot. That way you can PWM control the speed. This will be very important to walk in a straight line. My experience is that nothing goes straight without a little help, and PWM with relays is bad :-S Relay jamming and robot carrying does not sound fun. This can easily be arduino controlled from a radio receiver or wired controller
It would come to ~$20.60 for each motor
http://www.jaycar.com.au/productView.asp?ID=ZT2468
http://search.jaycar.com.au/search?w=2n2222&view=list
http://www.bristolwatch.com/ele/h_bridge.htm
Thoughts, feelings, flames?
Hally
I was at the space last night, it looked like they had the motor controller sorted
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Initially we were going to use a H-bridge/PWM to drive the thing, but ended up going with the Jaycar drivers and the relays, as Blair was having some trouble getting the H-bridge completed. @merseyless should be able to let us know what’s up with that.
As for moving, last night we got one side together. However it still needed some work, so I’m not sure what the status is at present.
Status is, one side is walking around and the majority of bugs are worked out. It won’t have a rider for the parade, but it will in the future. I’m building a chassis now, that’ll be one of the easier parts. it doesnt enjoy being pushed around but if you spin the crank it walks around clunkily but well. It will walk!
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Great work @rut4ger And all who put on such a effort to get this up and off the ground…
Do you need any help either on location or at the space tommorow?
Time would be handy if this is the case…
Tomorrow morning there will be a few crucial errands to run such as a nut and bolt shop if one is open early enough or bunnings. If someone could get here earlyish even just to do that it will save me a much needed hour.
I’ll be heading down from Redcliffe at 9 am. If there is a suitable place to buy the nuts and bolts I can stop by along the way. Alternatively I will be available to go and get the missing matetials after I get back yo the space at 9:30
The electronics are done. Cables still need to be run once the frame and chassis are ready. It uses a BTN7971B board. The firmware works and does everything it needs to, and 90% of what I’d ideally like it to do (I might tweak it if I get time). The BTN7971B board is controlled by an Arduino clone. User input is from an IBM compatible joystick. It runs off 12V.
Please don’t touch it, not even to ‘look’.
History on what happened:
These boards don’t seem to have a model name or number (the only markings are “DBK HT 2013.2.22”), but are built with 4 BTN7971B half H-bridge ICs, so I have dubbed them “BTN7971B boards”.
These boards look really good on paper, but are really picky and burn for no reason. James and somone else burnt one accidentally despite treating it nicely (using method 1 on the ebay item’s page - i.e. no PWM). I destroyed one (fixed it with spare parts from the first burnt one added extra flyback diodes and caps, then destroyed it again) while PWMing the enable pin - which is shown as being one of the allowable methods (method 3). PWM frequency was, I think, 500Hz; well below the 25kHz limit.
@merseyless & @rut4ger then resorted to buying 2 single-motor single-direction Jaycar speed controller kits and enough relay’s to build 2 H-bridges. @merseyless and I built the kits.
Shortly after we’d built the kits I got my hands on another BTN7971B board and after having a chat with Skip, a member of the Gold Coast Tech Space who has used these successfully before, determined what we were doing differently. Using “method 2” works. The BTN7971B ICs are pretty interesting, with a lot of built-in nicities: over-current (including short circuit) protection, over-temperature protection, built-in freewheeling diodes.
Also: even if a cheap arduino clone says it can go up to 20V input, it might still blow a cap at 12V.
I have an inkling why they burn using method 3, but not method 2, but I can’t find any confirmation or refutation on the net. I’ll model it later.
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Im in desperate need of help. I’m in my 22nd hour and the old noggin aint what she used to be. I can tell you how it goes together, I just need help getting it done.
I’d like to thank everyone who showed up to the parade. I counted 21 people (I think), which was a fantastic turnout! Reactions from the crowd were all positive, and the few people that asked about how long we had been working on the robot could barely believe it didn’t exist three weeks ago. I especially liked the way we were literally fixing, improving & upgrading things as a group while we were walking along during the parade - probably the best public demonstration of a hackerspace you could get. 
I know some people took photos & videos; I’d love to see them!
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^ Agreed Mike! It was an awesome turnout and effort by everyone, great work team!
I squished together some of the video and photos I took. This is not the finished product but just a start 
(please don’t link this video yet as its not currently hosted on the HSBNE youtube account. If you know the login for the HSBNE account please pm victor the details)
I was thinking it would be great if someone could start a photo / video blog for things happening at the space, if that isnt already a thing 
Hally
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Great video. I definitely think a frequently updated youtube account would help build up our presence.
Earlier this year I was keen on shooting a spoof of the viral Ken Block videos but instead of a modified Ford Fiesta drifting around a stock segway, Sam’s modified segway drifting around a stock Fiesta. With enough production value that could easily get us on Hackaday, /r/videos and maybe Youtube’s front page.
We have a blog, blog.hsbne.org. It’s also embedded on the home page. If you want to submit to it, go to the drop down next to the link to the blog in the header and select submit.
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All the Video (.avi) and the images (.jpg) that I took on the parade is currently being uploaded to dropbox and as soon as it is completed about 9 hours from now I’ll post the link.
For now here are some photos
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Finally here is the Dropbox link for most of Videos and all of the Images.
I’ll also have a few copies of all media I took at the event on DVD (4.4GB worth of Glamorous Sophistication!)
if anyone would like a copy.
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