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PetoiCamp / OpenCat-Old

A programmable and highly maneuverable robotic cat for STEM education and AI-enhanced services.
https://www.petoi.com
1.36k stars 362 forks source link

Suggestions for powering solution? #6

Closed borntoleave closed 5 years ago

borntoleave commented 6 years ago

I've been using 2S lipo batteries(7.4~8.4V) to directly power the servos. The servo's specification lists a maximal torque at 6.6V, but it works fine under 8.4V with some heating.

I hope to reduce the voltage to the safe 6.6V range. However when I connect some step down boards (9v to 6V, 3A max) in serial with the same 2S batteries, the output voltage will drop below 5V. It seems that the board will shutdown once peak current is higher than some threshold.

Do you know any cheap and neat solution to create a (6V, 5+ Amp) supply from the 2S lipo batteries? Thanks!

triffid commented 6 years ago

How about something like https://item.taobao.com/item.htm?id=563344121202 ?

On 22 May 2018 at 11:32, Rongzhong Li notifications@github.com wrote:

I've been using 2S lipo batteries(7.4~8.4V) to directly power the servos. The servo's specification lists a maximal torque at 6.6V, but it works fine under 8.4V with some heating.

I hope to reduce the voltage to the safe 6.6V range. However when I connect some step down boards (9v to 6V, 3A max) in serial with the same 2S batteries, the output voltage will drop below 5V. It seems that the board will shutdown once peak current is higher than some threshold.

Do you know any cheap and neat solution to create a (6V, 5+ Amp) supply from the 2S lipo batteries? Thanks!

— You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub https://github.com/PetoiCamp/OpenCat/issues/6, or mute the thread https://github.com/notifications/unsubscribe-auth/AAKBGgzy1KofxJ3Rq5jOqj0pl2z7PY1tks5t04bZgaJpZM4UH7F1 .

borntoleave commented 6 years ago

It has a problem: too large in both size and input voltage.

I have tested several step down board options, there seems to be a gap between 3A and higher current. Below 3A, the circuit can be made as small as a fingernail. Higher current boards will at lease triple the size. Any insights on that? 3A board 5A board

From the raw voltage(7.4A to 8.4V) to target voltage(6.6V), there's around 1V drop. And the current will be 4A to 5A. The power formula gives P = V*I = 5W. I'm not sure how to regulate the voltage without generating too much heat.

triffid commented 6 years ago

If 4A is enough, how about https://item.taobao.com/item.htm?id=546729706262

The seller would probably be willing to change them for you if you ordered a bunch

On 22 May 2018 at 12:35, Rongzhong Li notifications@github.com wrote:

It has a problem: too large in both size and input voltage.

I have tested several step down board options, there seems to be a gap between 3A and higher current. Below 3A, the circuit can be made as small as a fingernail. Higher current boards will at lease triple the size. Any insights on that? 3A board https://www.ebay.com/itm/10pcs-Mini360-3A-DC-Voltage-Step-Down-Power-Converter-Buck-Module-3-3V-5V-9V-12V/132416658988?epid=1402279667&hash=item1ed4a5de2c:g:VrUAAOSw8SpbAdyM 5A board https://www.ebay.com/itm/5A-XL4015-DC-DC-adjustable-step-down-module-buck-converter-4-38V-96/202216430664?hash=item2f1509dc48:g:6F8AAOSw-SBatssT

From the raw voltage(7.4A to 8.4V) to target voltage(6.6V), there's around 1V drop. And the current will be 4A to 5A. The power formula gives P = V*I = 5W. I'm not sure how to regulate the voltage without generating too much heat.

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/PetoiCamp/OpenCat/issues/6#issuecomment-390859953, or mute the thread https://github.com/notifications/unsubscribe-auth/AAKBGgc1T1Dfg_d460E4wkiUjpiHrg5Lks5t05WcgaJpZM4UH7F1 .

STGRobotics commented 6 years ago

I've been using the following two parts for my robots. they are small in size. Also I've run these batteries in series for more ah

Battery Tenergy Li-Ion 7.4V 2200mAh Rechargeable Battery w/ PCB (2S1P, 16.25Wh, 4A Rate) http://www.all-battery.com/li-ion1865074v2200mahrechargeablebatterymodulewithpcb.aspx or Tenergy Li-Ion 18650 11.1V 2600mAh Rechargeable Battery Pack w/ PCB (3S1P, 28.86Wh, 5A Rate, Samsung Cells) http://www.all-battery.com/li-ion18650111v2600mahrechargeablebatterypackwithpcbandbareleads-31494.aspx

Regulator Castle Creations CC Bec 10A 6S Switching Regulator https://www.amazon.com/Castle-Creations-Bec-Switching-Regulator/dp/B000MXAR12/ref=lp_6179585011_1_1?srs=6179585011&ie=UTF8&qid=1526992164&sr=8-1

STGRobotics commented 6 years ago

Tenergy sells whole for qty 100 or greater. http://www.tenergy.com/

borntoleave commented 6 years ago

@triffid Looks good. I‘ll order several for testing. Thank you!

borntoleave commented 6 years ago

@STGRobotics I'm using 2S EBL 18650/18500 batteries. I learnt that there's some regulation for shipping lipo batteries. For the first product, I probably won't include the batteries but will give recommendations.

STGRobotics commented 6 years ago

@borntoleave Have you look at using Amazon for shopping cart and warehousing.

borntoleave commented 6 years ago

@STGRobotics The kit will have tens of parts, and I have to preassemble some. I don't think Amazon can handle that for me.