#robotics Logs

Jul 23 2014

01:42 Hyratel1 huh. I just ran the numbers and here's how various battery chems cost per power (up front cost, not including charger or lifespans) - WH/$ ... NiCd = 0.444 ; NiMH = 0.632 ; SLA = 1.57 ; LiFePo = 2.56 .... note, that is for single cell modules of LiFePo, not assembled packs
01:43 rue_bed where did you find good prices on NiCd?
01:43 Hyratel1 robotmarketplace
01:43 rue_bed oh Wh/$
01:43 rue_bed so lio wins
01:43 Hyratel1 LiFePO
01:44 Hyratel1 by a LOT
01:44 Hyratel1 I was surprised
01:44 rue_bed so, how much for 14KWh
01:44 Hyratel1 note - this was going by the smallest capacity LFP cells on the site
01:44 rue_bed $5400 ?
01:44 Hyratel1 to give the worst possible case
01:45 rue_bed I need ~14kwh for the electric truck conversion
01:45 Hyratel1 http://www.electriccarpartscompany.com/30Ah-32V-3C-br-LiFePO4-Lithium-Prismatic-Batteries-br-HiPower-LiFePO4-EV-Battery-br-USA-Stock-br-40L-23W-64H-in-br-103-58-164-mm-br-26-lbs-12-kg_p_434.html
01:45 Hyratel1 only 3C though
01:46 rue_bed so, they can take 100A
01:46 rue_bed thats ok
01:46 rue_bed I'd need about 100
01:46 rue_bed of them
01:46 Hyratel1 actually, continuous discharge is 0.3C
01:47 rue_bed hmm 46Ah
01:48 rue_bed 14kwh/320V
01:48 rue_bed 46Ah
01:48 rue_bed those are 30Ah
01:49 rue_bed whats 70hp at 300V?
01:49 Hyratel1 for my own purposes, I need 100 A continuous at ~30-40 AH
01:49 rue_bed 52kw
01:50 rue_bed so peaking 162A
01:50 rue_bed everything points I should use 2 parallel banks
01:50 rue_bed 2p100s
01:50 Hyratel1 charging would be a bear
01:51 rue_bed $7200+chipping
01:52 rue_bed which isn't THAT bad, considering its 60Ah... 19kwh
01:52 rue_bed almost up to a tesla
01:52 Hyratel1 tesla uses 18650 cells though
01:52 rue_bed I wanted to do the whole conversion for less than $9000 tho
01:53 rue_bed yea, its 24kwh
01:53 rue_bed I cant get 19kwh of 18650 for $7200
01:53 rue_bed it comes out about $10000, even via aliexpress
01:54 rue_bed who's 18650 are 1.3 Ah, dispite whatever they label them as
01:54 rue_bed ( I got a few and tested)
01:56 rue_bed 103 * 58 * 164mm
01:56 rue_bed 1.2kg, 120kg, 240kg
01:57 rue_bed I wonder how much the gas system weighed
01:57 rue_bed hmm 70L of gas
01:57 Hyratel1 + engine weight
01:58 rue_bed and exhaust system and coolant system
01:58 rue_bed not much left of the sanoma after its power plant is pulled out
02:00 Hyratel1 hmmm
02:00 Hyratel1 electric gokart with 140 lb driver
02:00 rue_bed my motor plan is to gang vacuum cleaner motors
02:00 Hyratel1 24v will draw 30-40 A
02:00 Hyratel1 peak
02:01 rue_bed 70L is about 52kg
02:02 rue_bed so the gas alone makes for 43 lion batteries
02:04 rue_bed wonder how much a full rad weighs
02:04 rue_bed with a full overflow tank
02:06 rue_bed about another 7 lion batteries in rad coolant
02:07 rue_bed thats 50
02:07 rue_bed not inc the weight of the gas tank and radiator
02:07 rue_bed I think most of the balance is in how much the electric motor weights
02:08 rue_bed mine should be pretty light, vacuum cleaner motors are high rpm, verry high power to weight ratio
02:09 Hyratel1 what kind of vehickle is this
02:09 Hyratel1 and just buy a damn DC motor
02:10 rue_bed a 70hp dc motor would weigh about 700lbs and cost $10000
02:10 rue_bed 35 vacuum cleaner motors will weigh like 150lbs and cost $1400
02:10 Hyratel1 + all the rigging and chain, and the multiple points of failure
02:11 rue_bed sorry, the cost savings win
02:11 rue_bed I cant put $20000 into a truck I bought for $500
02:11 Hyratel1 https://dl.dropboxusercontent.com/u/33593534/images/Robot/DSCN2011.JPG
02:11 Hyratel1 this cost $600 in parts
02:11 Hyratel1 I don't want to hear it
02:12 rue_bed must be a gigapixel image, taking forever to load
02:12 Hyratel1 sorry bout that - brother's camera is fricken ridiculous
02:13 rue_bed Ithink I see an ant on one of the logs, its missing a leg
02:14 rue_bed oh that thing, yea, thats a nice build
02:14 Hyratel1 funnyman
02:14 Hyratel1 upgraded to a battery twice that size
02:14 rue_bed yea that looks lead
02:14 rue_bed gel, but still lead
02:14 Hyratel1 it is
02:14 Hyratel1 no, SLA
02:15 Hyratel1 flooded SLA
02:15 rue_bed that size (18ah).... runs my mowerbot for about an hour
02:15 rue_bed oh thats a 7ah
02:15 Hyratel1 that develops 1HP
02:15 MrCurious fghfghjfg: any luck with exciting the freeon through the concrete tensile strength using a forced freon matrix?
02:16 Hyratel1 we upgraded to an 18
02:16 rue_bed MrCurious, concrete-freon laser?
02:17 MrCurious oh my, i mispelled freon
02:17 Hyratel1 MrCurious, don't encourage him please
02:17 rue_bed I didn't notice, my autocorrect is on
02:18 rue_bed it automatically corrects things to whatever people meant to say
02:19 rue_bed I have to stop loading this image, before my computer crashes
09:41 Hyratel1 huh. I just ran the numbers and here's how various battery chems cost per power (up front cost, not including charger or lifespans) - WH/$ ... NiCd = 0.444 ; NiMH = 0.632 ; SLA = 1.57 ; LiFePo = 2.56 .... note, that is for single cell modules of LiFePo, not assembled packs
13:15 cambazz hello. any body experienced with brushless motors?
13:16 cambazz from what i understand one can set the torque, so whether it is a propeller or wheel it is turning, it wont need a gearbox? is this true?
13:17 Hyratel1 DC brushless ESCs actually set the RPM
13:17 Hyratel1 or rather, the phase rotation speed
13:17 Hyratel1 the RPM is derived from the number of poles per phase
13:18 Hyratel1 most hobby and robotics motors are three phase and I think 3-5 poles per phase
13:18 Hyratel1 so the RPM is phase speed in Hz /poles per phase
13:41 SquirrelCZECH_ cambazz: to certain degreee
13:41 SquirrelCZECH_ RC Cars brushless motors can change their ratio of torgue/max speed
13:41 SquirrelCZECH_ BUT, only to certain values
13:42 SquirrelCZECH_ cambazz: anyway, you should made it so, that it can work WITHOUT this settings
13:42 SquirrelCZECH_ and than tune it up with changing the ratio
13:45 cambazz well i was wondering if it is possible to use a brushless for a small differential drive robot with tracks. traditionally we would be using gearboxes, and an encoder.
13:48 SquirrelCZECH_ stick with gearboxes
13:49 SquirrelCZECH_ cambazz: I am using exactly this feature when I am racing with RC Cars
13:49 SquirrelCZECH_ it can really fine-tune it's behavior
13:49 SquirrelCZECH_ but good gear ratio is still base
13:53 cambazz ok i usually make threaded robots, small. this time i wanted to use an encoder gear motor
13:53 cambazz any recomendations
15:26 SquirrelCZECH_ cambazz: As far as I know you can use encoder on anything that is rotating?
15:26 SquirrelCZECH_ :)
15:26 SquirrelCZECH_ cambazz: well, for small robot
15:26 SquirrelCZECH_ I would stick with tamiya gearbox
15:27 SquirrelCZECH_ for bigger one, RC Brushless Motors and ESC with an gearbox 9:1
15:27 SquirrelCZECH_ got that in my old RC Car
15:27 SquirrelCZECH_ and it's able to go 90 degrees on wall
15:30 mumptai rc brushless motors for precise motions?
15:31 SquirrelCZECH_ define precise
15:40 cambazz SquirrelCZECH_ can you show me the gearbox?
15:41 Hyratel1 a servo is a gearmotor or other spinmotor with a positional feedback system in place
16:01 SquirrelCZECH_ cambazz: hobby king 1:9 gearbox I suppose?
16:01 SquirrelCZECH_ buyed the thing
16:05 Hyratel1 if you have a motor that won't slam into the endstops and can reverse hard without shredding either the gears or the driver chips, you can turn it into a servo
22:59 peepsalot what would be a low cost way to measure vehicle suspension positioning in realtime
22:59 peepsalot i thought a pot would be cheap but for a piston looking linear motion pot they are about $200 ea for the ones I see
23:00 peepsalot like this http://www.ebay.com/itm/Mychron-Linear-Style-Throttle-Potentiometer-150mm-/230536886521?pt=Race_Car_Parts&hash=item35ad11b8f9&vxp=mtr
23:01 Hyratel peepsalot, will there be mud/debris present on the system?
23:03 peepsalot it won't specifically be driven through mud, but there is possibility of dust,dirt,rain, puddles, etc.
23:04 peepsalot chunks of rubber and brake dust >:)
23:05 Hyratel so optic is not a viable solution
23:05 peepsalot unless it could be enclosed
23:06 GargantuaSauce use a string and a spring-loaded pulley and a rotary pot
23:06 GargantuaSauce quick and dirty
23:07 GargantuaSauce thread the string through a little hole in a dirt shield or the housing or whatever if necessary
23:07 Hyratel ^ this
23:08 peepsalot what kind of accuracy do you think that could give?
23:08 GargantuaSauce better than nothing
23:08 Hyratel Andymark has a multiturn pot kit towards that end
23:08 Hyratel http://www.andymark.com/product-p/am-2674.htm
23:09 GargantuaSauce you could also consider a little pneumatic cylinder and a pressure sensor
23:09 GargantuaSauce would need temperature compensation though
23:16 Hyratel peepsalot, how much accuracy do you need?
23:16 Hyratel what's your linear and angular travel
23:33 peepsalot not sure the suspension travel exactly, it would be actually on a car though