#robotics Logs

Jul 29 2015

08:57 codepython777 http://www.superdroidrobots.com/images/TD-044-240-B.jpg
08:57 codepython777 Whats the max stall current on this at 24V? 13A?
09:17 LiohAu codepython777: y
09:17 LiohAu that's what I read.
09:19 rue_house ohm -v 24 -p 34.7
09:19 rue_house Wattage is: 34.700001
09:19 rue_house Current is: 1.445833
09:19 rue_house Voltage is: 24.000000
09:19 rue_house Resistance is : 16.599424
09:19 rue_house how about not exposing it to more than 1.5A for prolonged shorts?
09:20 rue_house hmm that woldn't work
09:25 codepython777 Seems like 13A for 24V stalls
09:25 codepython777 LiohAu: Was trying to decide on a motor controller
09:25 codepython777 LiohAu: are there similar brushless motors you can point me to ?
09:26 LiohAu this one is brushed
09:27 LiohAu and at this price it's already good
09:27 codepython777 LiohAu: agreed
09:28 codepython777 LiohAu: wanted to see if i moved to brushless - what would i pay
09:28 LiohAu dont know. look at maxon website maybe
09:29 codepython777 maxon = cost arm and leg i thought?
09:30 rue_house brushless motors tend to have a min speed to
09:31 rue_house you cant creep them like brushed
09:31 LiohAu codepython777: alibaba maybe? :)
09:43 verak is almost finished with redesigng the X axis
09:43 veverak 3
09:43 veverak *i3
09:43 veverak well, one hell of a job
09:44 veverak but I should be able to put proper seals in front/behind bearings to prevent them from being destroyed by dust and etc...
15:50 emeraldgreen hi
15:55 deshipu hi emeraldgreen
16:01 emeraldgreen Has anybody building their own lipo charger? I have a pair of robots lying around because it bother me taking a lipo cell out of them and recharging it every time with standalone charger. I have searched quite a bit on this topic and haven't found any circuits for 3s1p (or any serial lipo for that matter) charging.
16:02 emeraldgreen Having an internal charger circuit that accepts unregulated 12v would be nice. From that it's not that hard to program automatic docking to charger.
16:03 wolfmanjm you can get breakout boards for lipo chargers from sparkfun and adafruit that would do the job
16:04 deshipu emeraldgreen: I usually use ready charging modules, but that's usually only available for 1S batteries
16:04 wolfmanjm deshipu: I'm having a lot of trouble with these UBECs, what do you use again?
16:04 deshipu wolfmanjm: let me see
16:05 wolfmanjm the 3a/5amax ones I got are realy 2amp they shutoff over 2amps
16:05 wolfmanjm so I needed two to run half the servos each. but I'm not happy with them.
16:05 emeraldgreen wolfmanjm I have found only single cell chargers there, it's hard to get an average-size hexapod working from a single cell. And I have 3S lipos anyway. Maybe you know wome 3 cell charging circuits?
16:06 deshipu wolfmanjm: I recently bought those http://www.aliexpress.com/item/Mini360-Model-aircraft-Power-step-down-module-Adjustable-DC-Power-Supply-Module-Ultra-Small/2030582894.html
16:06 wolfmanjm emeraldgreen: you need to balance charge them so you really need three separate 1S chargers :)
16:06 deshipu wolfmanjm: they are really tiny, but no idea about the specs
16:07 emeraldgreen wolfmanjm heh, I thought about dumb relays that connect thre cells in parallel to charge and in serial to work. I wonder how professional chargers do implement serial cell charging.
16:07 deshipu wolfmanjm: http://www.icstation.com/mini-buck-converter-step-down-475v-p-4056.html says 1.8A with 3A peak
16:08 wolfmanjm the standard chargers have three separate chargers nd charge each cell separately
16:08 SpeedEvil The most sensible suggestion is 3* http://www.ebay.co.uk/itm/5V-Micro-USB-1A-18650-Lithium-Battery-Charging-Board-Charger-Module-Protection-/371152022965 , three USB PSUs, and an AC extension to plug them into.
16:08 SpeedEvil (not really)
16:08 wolfmanjm deshipu: looks like these http://www.ebay.com/itm/10pcs-Mini-3A-DC-DC-Adjustable-Step-down-Converter-Standard-Power-module-LM2596-/171381728637
16:09 deshipu wolfmanjm: no, that one is much larger
16:09 emeraldgreen Maybe I should buy several single cell lipos and connect them in parallel and charge with a single charging circuit... Won't they go boom on me?
16:09 deshipu but probably the same chip
16:10 SpeedEvil http://www.ebay.co.uk/itm/B3-AC-100-240V-2S-3S-Li-po-Balance-Charger-For-7-4-11-1V-RC-Battery-/380744739703?pt=LH_DefaultDomain_3&hash=item58a627ab77 - slightly more seriously
16:10 SpeedEvil you could build this on
16:11 wolfmanjm emeraldgreen: my understanding (which is limited) is Lipos need to be charged separatley like with this... http://www.ebay.com/itm/261960479061
16:11 emeraldgreen wolfmanjm I use similar apparatus to do it, yes. But I need autonomy.
16:12 SpeedEvil emeraldgreen: you could simply put the charger on your device, and AC power the device
16:12 wolfmanjm then I agree with SpeedEvil three of those little charging boards should do it charge each cell individually
16:12 SpeedEvil That would need three isolated PSUs - which is silly
16:13 SpeedEvil emeraldgreen: What amperage is your cells?
16:13 SpeedEvil Ah
16:13 wolfmanjm right now I charge my 2S manually by hookin gup the charger to each cell with crocodile clips then when one is done switch to the other, it is a pain ;)
16:13 emeraldgreen SpeedEvil 1000mah
16:15 emeraldgreen SpeedEvil I could create a fancy dock with my battery's chrging socket and a relay system to unplug it from the robot while charging but it's be clumsy. I see that professional engineers somehow solve this problem in their mobile robots, so there should be a way. Maybe I should google more carefully about power manager ICs and schematics of roombas and AIBOs.
16:15 SpeedEvil http://www.ebay.co.uk/itm/Battery-BMS-Protection-PCB-Board-for-3-4-packs-18650-Li-ion-lithium-Battery-Cell-/181761482291?hash=item2a51d41e33
16:15 SpeedEvil This doesn't have balancing hardware - but it does have per-cell under/over-voltage cutout
16:16 wolfmanjm SpeedEvil: jackpot ;)
16:16 emeraldgreen SpeedEvil Nice
16:16 wolfmanjm that is actually what they have in laptop battery packs
16:17 SpeedEvil The laptop ones are better
16:17 SpeedEvil they have active balancing, as well as charge monitoring
16:18 emeraldgreen They use MM1414C IC, can't find datasheet
16:18 emeraldgreen Ah found it
16:18 SpeedEvil That would need in addition (for 1Ah cells) a 12.6V 1A constant voltage/current supply
16:19 SpeedEvil http://www.ebay.co.uk/itm/DC-DC-3A-Constant-Voltage-Current-Charger-CV-CC-LM2596-Step-Down-Charging-643-/221814905908?pt=LH_DefaultDomain_3&var=&hash=item33a532dc34 - plus a 15V or more laptop charger would be fine
16:21 emeraldgreen I see, maybe there are tested robot-specific circuits though, that surely won't puff my lipo. I could even settle with NiMh if charging them is easier.
16:21 wolfmanjm SpeedEvil: you used these http://www.ebay.com/itm/10pcs-Mini-3A-DC-DC-Adjustable-Step-down-Converter-Standard-Power-module-LM2596-/171381728637 do they actually handle 3amps continuous?
16:21 SpeedEvil I have not
16:22 SpeedEvil I would want to monitor the temp first time, and see if it needed a fanm or heatsink
16:22 deshipu wolfmanjm: they have 1.8A continous and 3A peak
16:22 emeraldgreen I used 10A buck DCDC in my hexapod but I can't find it on ebay anymore
16:22 emeraldgreen SpeedEvil thanks for your suggestions
16:22 SpeedEvil good luck
16:23 deshipu wolfmanjm: http://www.electrodragon.com/w/images/d/d3/MP1584.pdf
16:23 emeraldgreen Why don't people come up with open battery management system, it seems an obvious missing piece in DIY robotics
16:23 wolfmanjm ok so I need 3A continuous, and two of them to drive half the servos
16:24 wolfmanjm deshipu: is that the same as LM2596?
16:25 deshipu wolfmanjm: no idea, I just looked at the chip and looked for the datasheet
16:25 deshipu seems like it has 4A limit
16:25 deshipu 2.5W temperature dissipation
16:26 wolfmanjm yea looking at the specs now :)
16:26 wolfmanjm http://www.ti.com/lit/ds/symlink/lm2596.pdf
16:28 wolfmanjm seems 3amps is ok for that chip :)
16:28 wolfmanjm actually it would be 2.5amps continuous I think
16:28 wolfmanjm Lipos are a pain in the butt!
16:29 emeraldgreen wolfmanjm Do we have other battery tech?
16:29 wolfmanjm not that is light ;) I tried to use nimh but they are too heavy for my hexapod
16:30 wolfmanjm even the lipos only last about 15minutes
16:30 wolfmanjm that is if the UBEC doesn't cut out first
16:31 emeraldgreen In my hex they last for 30 mins of low activity, bec is not a bottleneck for me though
16:32 emeraldgreen Maybe I should ditch legged locomotion and build simple wheeled base with a pair of arms
16:33 deshipu emeraldgreen: I have one LiFePO4 battery, it's nice
16:33 deshipu emeraldgreen: and about as heavy as a lipo
16:34 emeraldgreen deshipu Looks chargers are as complex for them as for lipos.
16:38 emeraldgreen http://www.batteryspace.com/Smart-Battery-Systems-SBS-with-SmBus-V1.1-support-for-14.8V-6.4Ah/10Ah.aspx
16:39 emeraldgreen >4.3V ± 0.025V
16:39 emeraldgreen Is it really safe
17:37 wolfmanjm heh most of the regulators on ebay saying they are LM2596 are not using that chip at all
17:40 emeraldgreen wolfmanjm Ebay stuff is weird, it can work OK but if you don't download a circuit while it's there you can lost it forever
18:25 orlock http://www.damninteresting.com/on-the-origin-of-circuits/