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mark_m
Joined: 23 Apr 2005
Posts: 23
Location: Cambridge, uk
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Progress!
Woo hoo! It rolls!
Just had the best lunch break ever, 20 minutes of driving practice.
Here's a link to a video from last nights test drive:
http:///www.hyperdynamic/images/robots/VyrtTest1.avi
Sorry, it's ~25Mb I need to find out how to compress it.
I'm getting about ten minutes of driving off a single pack, which I'm really happy with. At the moment I'm using a resetable circuit breaker (30amp) to protect the whole system. It's not tripped yet so I might lower that and see what happens.
I think the relays are sticking on one side, sometimes I only have reverse on one side, other times I only have forward. If I stop and fiddle with the wires, it swaps
I've also noticed some of my screws are coming loose. They're M4x16 going into edge tapped 10mm polycarbonate. I'm going to get some M4x 25 but I want to thread lock them somehow. I know loctite messes with poly so what can I use?
Tyres are wearing down worryingly quickly, hopefully they won't wear down as fast on plywood arenas, I've got some MDF at home I'm going to have start using for testing. In the vid you can see I'm practicing in a carpark and the tarmac's really rough.
Next ups the weapon and some armour.
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Mon Jan 28, 2008 11:35 pm |
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mark_m
Joined: 23 Apr 2005
Posts: 23
Location: Cambridge, uk
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relay arching
The relays are wired as per the technobotys datasheet:
http://www.technobots.co.uk/Data%20Sheets/1500-021.pdf
The relays are the 30amp ones that came with the electronizes.
No resistors, no capacitors, no diodes. the entire wiring diagram is in my post earlier in the thread) I've followed some threads on quenching arcs, but I thought that since my stall current should be less than the relays continuous rating, I should be ok. I suppose the current during reversals could be higher, I'm not sure. I had major relay problems on my last but but that was 9.6V drills on 24V in a 5kg robot.
Can you determine motor inductance using a scope? I've got quite a few different diodes and most resistors on hand but I've only got a few electrolytic caps so I guess I'm going to have to buy some none polarised ones. Can anyone suggest a good starting point as I've not sized anything like this before.
The datasheet suggests a 1uFarad cap for 28V, 5Amp but that doesn't seem to be based on either the inductance or the current, which seems a bit odd.
I've just realised I've got no caps on my motors either, could you suggest a suitable size for those too?
Thanks for the help
Mark
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Tue Jan 29, 2008 3:27 am |
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