RC ESCs instead of an h-bridge.
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Ok Ive been doing a ton and ton of back and forth and thinking about this, and ive come down to either a 4wd Rover5 with Dagu off road wheels and l298 h-bridges.
The second choice is a sting ray, but If i go with a 2 wheel bot like the sting ray I really want it to be compatible with the boe bot, that way I can use the plethora of information written for the boe bot to learn from. Theres even prop based boe bot tutorials on learn.parallax.com. I know the boe bot just isnt going to be enough for me in the long run though! So in order to make the sting ray more boe bot compatible ive been looking at every solution, including things like using an ATTiny to convert RC Servo Style pulses to true PWM and connecting that between the bs2/prop and the h bridge.
Well I ran across these http://www.hobbyking.com/hobbyking/store/__6455__Hobbyking_SS_Series_8_10A_ESC.html now if I were to buy two of these would these be suitable for driving the sting rays motors using the RC servo pulsing in the book? Also the sting ray motors are 4.5amp 7.2 volt, these ESC's are rated in cells, im not sure if that is lipo cells or what... but ill be using nimh, as Iv already built a nimh charger for this project and own a ton of 2500mah nimh cells
The second choice is a sting ray, but If i go with a 2 wheel bot like the sting ray I really want it to be compatible with the boe bot, that way I can use the plethora of information written for the boe bot to learn from. Theres even prop based boe bot tutorials on learn.parallax.com. I know the boe bot just isnt going to be enough for me in the long run though! So in order to make the sting ray more boe bot compatible ive been looking at every solution, including things like using an ATTiny to convert RC Servo Style pulses to true PWM and connecting that between the bs2/prop and the h bridge.
Well I ran across these http://www.hobbyking.com/hobbyking/store/__6455__Hobbyking_SS_Series_8_10A_ESC.html now if I were to buy two of these would these be suitable for driving the sting rays motors using the RC servo pulsing in the book? Also the sting ray motors are 4.5amp 7.2 volt, these ESC's are rated in cells, im not sure if that is lipo cells or what... but ill be using nimh, as Iv already built a nimh charger for this project and own a ton of 2500mah nimh cells
Comments
Enjoy!
Mike
inbetween than what they were a couple of years ago.
It would appear to me that Brush type DC hobby motors will not be available in a few years.
It's just a thought
Id been thinking about just doing a DIY ESC, something like a prop/avr connected to an h bridge that converted the RC pulse's to the micros native PWM, but thats a project with in itself as I cant seem to find a simple open source project with the code already written.
http://www.ebay.com/itm/RC-10A-ESC-Brushed-Speed-Controller-for-1-16-24-for-Car-Boat-Tank-w-brake-/251194596108?pt=LH_DefaultDomain_0&hash=item3a7c5d5b0c
The main concern is I keep reading alot of ESC's have a safety feature that wont let you go from forward to reverse instantly, but this has tank in the recommended uses which uses differential drive.
Now would I be able to basically plug two of these in to a bs2/prop then connect them to the sting rays motors and basically have a big/fast boe bot, or would I have some other issues I may be over looking?
"The main concern is I keep reading alot of ESC's have a safety feature that wont let you go from forward to reverse instantly, but this has tank in the recommended uses which uses differential drive."
I don't understand why you think this is a bad thing! If you are using a gearbox motor that is using 10 amps; you want your motor to come to a stop before you go into reverse! If you didn't, your gearbox would have broken gears in no time. You would also fry your motor controller in no time. Remember that your controller would not only have to handle the watts that you are giving it when you put it in reverse but also all the watts the motor has stored when it was moving forward.
Al
Agreed!
I don't think it's worth bothering to use an ATTiny to convert hobby servo pulses to PWM signals. This is trivial for the Propeller to handle.
I've been actively working on code to control four motors with one cog. I'm pretty sure it works just fine. I'll post an updated version in the Rover 5 thread tomorrow. I'm using the code with L298N motor controllers in one robot and Pololu's MC33926 boards in another.
Right now the code uses three I/O pins per motor but this should be able to be reduced to two pins per motor with a little additional hardware (an inverter (or maybe diodes (right erco?))).
Code for controlling two motors with PWM (with a Propeller) is very common.
I do agree that CR servos are easier to use than regular DC motors but not by much. While I think the HB-25s are nice motor controllers, I don't think they would be the best use of your limited robotics budget.
So do you guys totally disagree with using something like this
http://www.ebay.com/itm/RC-10A-ESC-B...item3a7c5d5b0c
instead of just using a standard h-bridge?
Inverter is the way to go. IIRC you'll fry the 298 if your code accidently makes both inputs high.
I just got my ghetto mecanum bot running last night with twin 298s... that thing's a hoot. Working up a video.
rwgast, I'm cleaning up my four motor PWM code right now in order to post it to the forum. I'll add a method with same type of interface as the servo method so instead of using -1000 to 1000 speed setting wth zero as stop, the method will accept input like a normal servo with 1500 as stop.
This should make using code for the BOE-Bot easier to use with an H-bridge motor controller.
I also don't see anything wrong with the speed controller from ebay. It would save you one or two I/O pins per motor.
I'll add inverters to my next parts order.
I want to see that video!
Check this 4069 hex inverter from RADIO SHACK: 99 cents, free ship. Now you're barkin'! http://www.ebay.com/itm/NTE4069-CMOS-Hex-Inverter-High-Voltage-Type-NTE4069-/360571143242
Me too. Might have Youtubed it yesterday, but for a sick toddler puking through the night... but the delay bore unexpected fruit. I shall produce a video, the likes of which have never been seen before!
... on my Youtube channel anyway.