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James2



Joined: 07 May 2015
Posts: 115
Location: South Australia


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or if they go in to a pit.

Post Fri Jan 27, 2017 4:23 pm 
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NMO
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Joined: 16 Jun 2004
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Location: Melbourne


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Fryddog, what's the current specs of your arena? Size, floor and roof material and thickness, polycarbonate thickness?

Post Fri Jan 27, 2017 9:16 pm 
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Fryddog



Joined: 24 Sep 2015
Posts: 75
Location: Adelaide


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Our arena is 1.2m by 1.2m with 100mm high walls. The two pits are 150mm x 150mm, each with a trap door that is activated by an electromagnet. The arena is built from 12mm chip board flooring. Under each pit is a small MDF box with padding and a little clear polycarbonate hatch for removing bots. The trap doors also have servos for resetting (haven't got them working well yet). The arena is held up by legs taken from two cheap Bunnings sawhorses (folds up nice!).

The shield is 3mm thick polycarbonate, held together by some 3mm thick aluminium angle. The angle is a little longer than the shield panels so that it can sit snug outside the arena walls. On two opposite sides are polycarbonate hatches for access and another hatch up higher for access to the GoPro.

The roof lid is made of 12mm MDF, also 1.2m by 1.2m, with 100mm high side walls to hide the downlights. There are 5 12V LED downlights (red, blue, green, yellow and white), each downlight is controlled by the Arduino system. We've also got some mounts and wiring for a couple of LCD monitors for streaming the GoPros when we were at Maker Faire last year.

Let me know if you'd like pictures.
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Post Fri Jan 27, 2017 9:54 pm 
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NMO
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Joined: 16 Jun 2004
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Location: Melbourne


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Thanks fryddog,

How high is the polycarbonate? 600mm?

Pics would be great

Post Fri Jan 27, 2017 10:02 pm 
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Fryddog



Joined: 24 Sep 2015
Posts: 75
Location: Adelaide


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The poycarbonate is about 1.1m high. A bit overkill but I was going for a nice and high lid which goes well with the downlights.

I'll post some pictures tomorrow or Sunday, after our meet.
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Post Fri Jan 27, 2017 10:13 pm 
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NMO
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Joined: 16 Jun 2004
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Location: Melbourne


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So been thinking a lot about the arena.

I was looking through my junk box the other day and came across a USB to servo interface board for 12 servo's (more than enough for the arena.)

https://www.pololu.com/product/1352

At this stage the plan is for 2 pits, each controlled by 2 servo's (a locking arm, and a reset arm to move the trapdoor back to closed)

A analogue countdown timer that will also use a servo,

Heres a 3d model of it, Im printing a sample now.




Also been thinking about some brushed ESC's to control the arena lights, also via the servo controller.

The plan will be for a laptop to control the arena as previously mentioned, version one will just control the arena.
version two will control the arena and the match draw.

Post Wed Feb 08, 2017 7:53 pm 
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NMO
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Only printed in draft, so need to reprint, but is works.

Post Thu Feb 09, 2017 5:34 pm 
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Fryddog



Joined: 24 Sep 2015
Posts: 75
Location: Adelaide


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Looks cool! The count down timer is a cool idea. We don't have one yet, instead our arena makes noises and flashes coloured downlights at 1, 2 and 3 min intervals.

Our pits have had two different release mechanisms which might give you different ideas as apposed to a servo release mechanism:
- The first was some door solenoids. These had a habit of getting stuck if a few bots sat on the trap door, creating too much friction for the solenoids. We also found that they tended to make too much volt drop when activating and sometime reset the Arduino system (fixed with some free wheeling diodes).
- The second method which we are using now is some electromagnets. They are 12V and switched by some solid state relays which are controlled by the Arduino. These work well except that they are a bit underrated - I bought 2kg ones by mistake. When we had more than one bot sitting on the trap door or a bot wass putting a lot of force downward, it sometimes released prematurely. This will be easily fixed with a couple 5kg electromagnets instead.
- If you went with a servo mechanism, you'd have to select servos with a lot of torque to overcome any force put on by bots potentially sitting on the pit doors. These can get very expensive as you know. A solenoid is a cheaper option and an electromagnet is cheaper again.

For the resetting option, we're trialing this out now but with not much success. We used two standard servos rated for around 20kg/cm torque (I forget exactly). They were mounted on some 3d printed brackets and with 3d printed arms to attach directly to the servo horns. Everything held up okay except the servos which were underrated and are now ruined ($120 wasted!). I still love the servo idea and will improve on it but I would suggest going overkill with the servo selection or coming up with some awesome mechanical mechanism for it (which is a bit beyond my skills).

Good luck! I'm keen to hear what you come up with and I'd love suggestions that could improve our arena!

Also sorry, I haven't gotten photos of our setup yet.
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Post Thu Feb 09, 2017 6:24 pm 
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NMO
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Joined: 16 Jun 2004
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Location: Melbourne


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I do like the idea of electromagnets, Ive just grabbed 2 off ebay,

I have a few ideas, I'm planning on controlling arena lights with 2s-4s brushed esc's, Just the cheap ones off ebay. That way, everything is controlled by the servo control board and only one interface to the PC.

Im still thinking through driver ready buttons, Driver tap out buttons, the servo control board can be configured for inputs, I think that will be stage 3 though.

If we have judges then they can ask those questions and enter them into the laptop

Post Thu Feb 09, 2017 7:15 pm 
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NMO
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Joined: 16 Jun 2004
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Location: Melbourne


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Might also think about old world servo microswitches, meets 3d printer frames

http://www.thingiverse.com/thing:1036357

Post Thu Feb 09, 2017 7:32 pm 
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NMO
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Joined: 16 Jun 2004
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Location: Melbourne


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Been thinking more about the trapdoor,

servo's, electromagents, but what about linear actuators?



Excuse me bad cad, Red is the arena floor and actuator support,
light blue is the trapdoor clised and the actuator extended
dark blue is the trapdoor open and the actuator closed.

$44 on ebay for a 12v one.

Post Mon Feb 13, 2017 4:41 pm 
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NMO
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Joined: 16 Jun 2004
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Location: Melbourne


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I purchased timber for the arena base yesterday, the external dimensions of the arena will be 1 x 1 meters, 1.2 was the plan but it doesn't fit in the back of the car (Nissan xtrail)

Post Sun Feb 19, 2017 7:59 am 
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Valen
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Joined: 07 Jul 2004
Posts: 4425
Location: Sydney


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They are normally pretty slow aren't they? might be a good thing though, adds dramatic tension ;->
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Post Sun Feb 19, 2017 8:23 am 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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You can get around that by attaching the actuator really close to the hinge - that way a small actuator movement will have a large effect on the trapdoor.
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Post Sun Feb 19, 2017 9:13 am 
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Fryddog



Joined: 24 Sep 2015
Posts: 75
Location: Adelaide


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How's the arena coming along? Reckon you'll be doing any Antweight meets in the near future?
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Post Tue Apr 25, 2017 10:13 am 
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