RCroller shooter
In order to dribble and shoot the ball each robot needs a roller and shooter device. There are several methods to accomplish this as of yet none have been chosen.
Contents
The Wall
07/09/06 - Scott, see the RobocupVision page. I talk about framerates etc. --Andy 14:36, 9 July 2006 (EDT)
07/04/06 - I like the rail gun idea, and I tried doing it once with no success. But look up info on solenoids, they are probably the easiest to build. Essentially all you need is a coil driver of some sort, its essentially a chip, I've posted some on this page so look there. You can connect the chip into the circuit and it acts a switch. We can dump charge from the capacitor through it and ito the inductor. But yeah keep looking and be sure to post stuff here --Phillip 12:17, 4 July 2006
07/02/06 - Just shooting off some ideas here. I read that the CMU team uses three(!) charged capacitors at 200V to drive a custom solenoid and that their shooting can hit the ball at around 35mph... that's ~ 51.3ft/s, 15.65m/s, or 1565cm/s. Do we even have a camera in mind that can capture anything near that fast? More importantly, do they, really? It says they have the smallest 3CCD "prosumer" camcorder from sony... I really don't think that's a crazy-fast FPS camera, so perhaps that's something to consider (that is, worrying more about where the ball is likely to go rather than where exactly it is while the other team has it). As for the shooter itself, I don't know much about solonoids, but I'll be looking those up soon. I did, however, have a quick idea about what we might could do... I don't know how feasible it would be, but maybe a small device that acts somewhat like a rail gun could be used. We'd take a small metal rod, hook it up so that it can't shoot out the front of the robot, then put it in a tunnel of small coils connected to some capacitors. When the capacitors drain, the coils would propel the rod like 1-1.5 inches out of the robot to hit the ball. It's probably not practical by any means... so I'm looking into other possible solutions as well. ;) -- ScottT 11:21, 2 July 2006 (EDT)
Capacitor Data
This a link to Capacitors from CDE that are electrolytic and photoflash. The sell high-power capacitors. Don't check digi-key, they don't sell high power.This is a spec sheet for the capacitor we are thinking about.
The part number for our particular capacitor from CDE is 7P122V330A052. It is a 1200uF capacitor rated at 360V that we plan to run at 300V
We based our calculations on the following:
.05 kg -- mass of golfball
35 mph -- final ball velocity
5.62 J -- energy to shoot the ball
If we assume 10% efficiency from the capacitor to the ball then
we need 56.2 J in the capacitor. So we need
1244.4 uF capacitor (E = .5*C*V^2; running at 300V)
If the robot operates at 7.2V and 80% efficiency into the capacitor then
it draws .98A continuously to fire every 10 sec
Capacitor Charger
- Linear Technologies Crappy website which doesn't allow permalinks. But, wide selection, good app notes, the only offerings which can handle our (relatively) high system voltage (9.6 VDC). Samples ordered of the LT3485-3 and LT3585-3. These parts should charge the caps quicker then others, but a a reduced efficiency ~80% in comparison to Linear's other offerings. Probably gonna use one of those two.
- Allegro
- TI
- Zetex
To Do
- Determine how roller and shooter will work
Specs-Shooter
| Device | Driver for shooter |
|---|---|
| Drive Power | ? |
| Logic Voltage | 3.3V |
| Configuration | Low-Side |
| Package | SOIC or PO-SOIC |
Schematics
Schematics
Shooter Drivers
- TI Solenoid driver, Overcurrent protection, 3A
- TI Solenoid driver, Overcurrent protection 2.7A
- ST Micro Dual Switch mode Solenoid Driver, 2.5A@40V
Notes
Next year
- Include a fuse
- Include a bleeder resistor
