Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Bajanick on November 19, 2007, 11:48:51 PM

Title: Is this a good choice for my needs?
Post by: Bajanick on November 19, 2007, 11:48:51 PM

I have a electric wheelchair I will be using as a base for a rover. I need an Hbridge or motor controller that can whithstand at least 60 amps under normal load.
Can I get away with using this (in the link) type of solenoid for the control of the motors? I know there will be no speed control.

http://www.allelectronics.com/cgi-bin/item/SOL-80/500050/12_VDC_POWER_SOLENOID_.html

Title: Re: Is this a good choice for my needs?
Post by: airman00 on November 20, 2007, 09:23:26 PM

remember to search the forum

http://www.societyofrobots.com/robotforum/index.php?topic=1904.0 (http://www.societyofrobots.com/robotforum/index.php?topic=1904.0)


My blog has some info on using wheelchairs also.... erobots.blogspot.com (http://erobots.blogspot.com)

,Eric


P.S. The solenoid you posted is overkill for a wheelchair motor

Title: Re: Is this a good choice for my needs?
Post by: Admin on November 20, 2007, 10:10:42 PM

For a heavy robot you'd definitely want speed control - otherwise the jerky motions will break stuff . . .

I quickly browsed around and found these rated at 60A and 120A:
http://www.robotmarketplace.com/marketplace_ifi_esc.html

I'm sure there are plenty more:
http://www.societyofrobots.com/robot_parts_list_electronics.shtml

Title: Re: Is this a good choice for my needs?
Post by: airman00 on November 21, 2007, 09:45:55 AM

i agree,

i will add speed control to my butler robot ,

without speed control its not very smooth and it does break stuff ( if things are loosly mounted..)

Title: Re: Is this a good choice for my needs?
Post by: Rebelgium on November 21, 2007, 02:37:59 PM

not to mention that those sudden starts reaquire huge currents...
which isnever a good thing when working with batteries. (not without batteries either for that matter  ;))

Title: Re: Is this a good choice for my needs?
Post by: Bajanick on November 22, 2007, 11:23:40 PM

Ive seen those ifi and vantec controllers but they are pretty expensive. I know I will have a hard time with my budget.
I originally was going to use a vantec that you can hook up an RC directly to but its too much money.
I thought about the auto relays but I cant see how they could handle the startup draw and the stall current, would they?

Thanks.

Title: Re: Is this a good choice for my needs?
Post by: Admin on November 23, 2007, 05:52:50 AM

The dimensionengineering.com (http://www.dimensionengineering.com) motor drivers can also do RC input, and are much cheaper . . .

Title: Re: Is this a good choice for my needs?
Post by: airman00 on November 23, 2007, 06:31:33 AM

i've used automotive relays on my butler robot and they work fine .

Speed control is the best though.

Look on my blog erobots.blogspot.com

it has info and a video of a robot which uses wheelchair motors and automotive relays . I used two 12V   20Ah  batteries - -and i get a really really long lifetime per charge

Title: Re: Is this a good choice for my needs?
Post by: Bajanick on November 24, 2007, 12:20:05 AM

I cant see how 30 amp auto relays can withstand the startup current and a stall current of 80 amps or so. When I get a chance I am going to do some tests. Ive seen the dimensions engineering site but they dont have any high current controllers.

Title: Re: Is this a good choice for my needs?
Post by: nathan25 on November 24, 2007, 12:39:05 AM

HAve you thought about going to an old scrap yard and looking for an electric car?
you could probably find what your looking for and evn hav speed control.

Title: Re: Is this a good choice for my needs?
Post by: bens on November 24, 2007, 01:01:58 AM

You can use two 30 A VNH2SP30s (http://www.pololu.com/products/pololu/0707/) to make a single 60 A H-bridge (assuming you can cool them enough for them to operate at their maximum current ratings), though that's still a little short of your 80 A stall.  The dual half-bridge configuration is described on page 14 of the VNH2 datasheet (http://www.pololu.com/products/pololu/0707/vnh2sp30.pdf).