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BotsIQ Training October 24 & Nov. 7, 2008

BotsIQ Training October 24 & Nov. 7, 2008. Batteries Motors Drivetrains. 5.1 Robot Electrical Systems. A BotsIQ robot could have two general types of electrical systems. a. Primary-Power (high current) is used to move the robot and actuate the weapon system.

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BotsIQ Training October 24 & Nov. 7, 2008

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  1. BotsIQ TrainingOctober 24 & Nov. 7, 2008 Batteries Motors Drivetrains

  2. 5.1 Robot Electrical Systems • A BotsIQ robot could have two general types of electrical systems. • a. Primary-Power (high current) is used to move the robot and actuate the weapon system. • b. Secondary-Power (low current) could be used to activate the remote control receiver. (battery or voltage converter)

  3. 5.2 Voltage Limitations • a. 24 volts DC, with full charge 28 volts • b. AC cannot be used

  4. 5.3 Electric Power Sources • 5.3.1 Allowed Battery Types • Only commercially available, rechargeable batteries of the following types can be used: • a. Sealed-Lead (provided that they are leak-proof) • b. Nickel-Cadmium (Ni-Cad) • c. Nickel-Metal Hydride (Ni-MH) • D. Lithium-Ion (Li-Ion) • LITHIUM POLYMER ARE NOT ALLOWED

  5. 5.3.2 Battery/Capacitor Mounting • Primary-Power batteries and any electrolytic-type capacitors have to be securely mounted and located so that they are enclosed within the structural frame of the robot.

  6. 5.4 Electrical System Requirements • The electrical system has to be designed and constructed to minimize the possibility of a short circuit or electrical arcing.

  7. 5.4.1 Primary-Power Wiring • a. Multi-stranded wiring is used for connecting the primary-power batteries to the input of the master switch. • b. Exposed terminals and bare wire-ends from the primary power batteries to the input of any master switch are covered with electrical insulation. • c. All wires are insulated with factory insulation, heat-shrink tubing, electrical tape or electrical liquid tape coating. • Non-electrical tapes (duct,masking) cannot be used.

  8. 5.42 Primary Power Master Switch • Primary-power electrical system is required to have a Master switch or a combination of Master switches. Each switch has to: • a. Directly shut off power from the primary-power batteries, and not indirectly shut off power using a relay or contactor. • b. Be completely mechanical, without any electronic components • c. Be a two-position that is stable in on and off positions • d. Be enclosed type, so that any arcing will occur on switch interior • e. A removable link may be used in lieu of a Master Switch if the link complies with all of above requirements.

  9. 5.43 Secondary Power Deactivation • If the secondary-power system has an on-off switch, the switch has to be positioned such that it can be operated without placing any body part in the path of any weapon system or other powered moveable part of the robot.

  10. GOOD MASTER SWITCH • Compact , light weight, positive and impact resistant. • Example: Team Whyachi # MS-05 (www.teamwhyachi.com)

  11. Battery Requirements • Voltage – determined by motor selection. • Series vs. Parallel – • a. 2 -12 volt/ 3000ma. batteries placed in series will result in an output of 24 volts and 3000ma. • b. 2-12 volt/3000ma. Batteries placed in parallel will result in an output of 12 volts and 6000ma.

  12. Battery Current Rating • 1000mah is the same as 1.0 Amp Hour (1000ma = 1 ampere) • “Amp hour” rating are used to describe how much current can be extracted in a one hour time frame. • A 3000mah battery will deliver 3 amps continuously for one hour or 1 amp for three hours.

  13. About “C” Ratings • “C” is a 1000:1 ratio of the capacity of a cell or pack in mAh to a given current. • Example: A 1500 mAh battery is rated to have a Max. discharge of 10 c. (1500/1000 x 10 =15) IE this battery is capable of discharging at a rate of 15a. • The higher the “C” rating the more discharge potential. • “C” rating can be either intermittent or continuous.

  14. Battery Energy Density • The energy density of a battery is the ratio of its stored energy to its weight of volume. High-energy density batteries provide more capacity in a smaller package. • Batteries with a high energy density are lithium-ion and nickel metal hydride.

  15. Battery Charging • Batteries need to have an approved charger for the type of battery and the number of cells. Consult a battery dealer for a suitable charger. • Lithium-ion batteries are recommended to have a charger with a balancing feature. • Factors to consider when purchasing a charger are: time required to recharge the battery. (remember that you may have as little as 15 min. between rounds) and having a spare battery pack.

  16. Battery Safety • Batteries can reach very high temperatures as they discharge. Be extremely careful when removing at the end of a match not to get burned. • Don’t overcharge or overheat the battery during the charging process. • Protect batteries in the robot by securing them so that they aren’t bounced around. • Plan on having an extra battery capacity to last for a 4 minute round. (batteries will lose their power capability as they age)

  17. Battery Supplier Web Sites • www.battlepacks.com • www.robotmarketplace.com

  18. Hardware/Parts Suppliers • www.mcmaster-carr.com • www.hobbylobby.com • www.banebots.com • www.sdp-si.com

  19. 5.5 Electric Motors • 5.5.1 Electric motors used on BotsIQ robots can be of any type, including DC or AC, brushed or brushless. Permanent magnet, series or parallel wound. No restrictions on the physical size or power output. • 5.5.2 Motor Cooling • a. Internal and external cooling is allowed and recommended. • b. Heat sinks are allowed but cannot be connected to any pneumatic component. • c. Liquid cooling is not permitted.

  20. 5.6 Electromagnets • Externally-mounted electromagnets can be used provided that: • a. The electromagnet if powered only by a DC voltage, may be switched on and off, or reversed in polarity. • b. The control electronics for the electromagnet does not interfere with any robot radio control signals or communications equipment.

  21. Motor Considerations • Size • Voltage • Mounting capability • RPM/volt • Current required • Speed controller required • Gear box (metal vs. plastic gears)

  22. Calculating Robot Speed • 1. Determine from specifications the no load rpm of a motor and estimate the load speed of 50% vs. no load. • RS-540 motor has a no load of 16,800 • 16,800/2= 8400 rpm • 2. Calculate gear reduction (16:1 25:1 etc) • 8400/16= 525 rpm • 3. Convert rpm to revolutions per second (rps) • 525/60= 8.75 rps • 4. 8.75 x wheel dia. (2in) x 3.14= 54.95 in/sec • 5. Convert in/sec to mph 17.6 in/sec = 1 mph • 54.95/17.6= 3.12 mph

  23. Factors affecting speed calculations • Drive train friction • Motor efficiency • Available voltage • Wheel diameter • DO YOU WANT SPEED OR TORQUE???

  24. Motor Issues • Mounting screws • a. Internal • b. external • c. Phillips vs. socket or torx head • d. Flat head vs. pan head

  25. Drive Trains • Web sites to visit for drive train design examples: • www.teamcosmos.com • www.Sites.bergen.org/battlebots • www.Mirobotics.com

  26. Motor Mounting Issues • 2 - 3mm screws that attach inboard end plate to motor work loose. • Need 4 mounting screws, 2 don’t work. • Need to design in order to have a quick change.

  27. Good Resources • www.banebots.com motors, speed controllers, wheels • www.hobbylobby.com ( motors, speed controllers, chargers, power supply) • J&C Hobbies 412.795.9344 Penn Hills and the Mills Mall • McMaster-Carr (hardware, belts, metal) • www.onlinemetals.com aluminum/ steel • www.sdp-si.com (aluminum pulley, belts • Multi-metals Greensburg, PA 724.836.2720 • Rick Volker volkerr@pbsd.k12.pa.us

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