Axe Related Questions.

[shakesc]

GR-02 s will do as well as a speed 900 both on 12v.
and sorry Gary I didn't include the import tax

Can you expand further on what you mean by this

[archie2000]

they both have there benefits and the 12v GR-02 will do more watts than the speed 900s however the speed 900s can take a higher voltage so they can go up to 24+volts where GR-02s shouldn't go above 18.
its my personal opinion that the GR-02s look rugged. light. small and powerful.

[archie2000]

so anyways,
I just sketchupped a robot that I was hoping my featherweight to look like.
Its increadibly bonxy (which was part of my inspiration) but I need to know how to change it to make it look more origianal- like an axe which I was hoping to stick on last.

[archie2000]

Sorry for posting 3 in a row again but I found this
RC dual motor controller for under $10
http://letsmakerobots.com/node/10509
Could this be scaled up and used in more than 4 amp bots?
Thanks

[Merkabah_PT]

That's a good idea, using 2channels together do double the capacity, and then stacking another IC to double it again.
I think it will work fine, and you can stack even more IC's to handle even more amps.
But you would need a PIC or atmega with custom programming to transform the signal from the RX to PWM so that the H-Bridges could understand.

Like Typhoon-Driver sayed in another post, building your own ESC is very difficult and many times more expensive than buying one, and theres the possibility of it never working.

If you are on a budget, you can make 2 h-bridges using relays and servo PCB's.

[archie2000]

I already have botbitz tz-85s for my robot I was just curious at this after looking for days and finding nothing about building ESCs last year.
I have made it less bonxy
Also if you live near Birmingham here is some REALLY cheap steel
http://www.ebay.co.uk/itm/MILD-STEEL-PL ... 43b913c1d2
Thanks

[Merkabah_PT]

If you search for RC cars diy esc you can find some sites with diagrams, parts list, etc. I also thoght about building 2 for my robot, but i abandoned the idea.

[marto]

Re: The Picaxe 8A motor driver.

Seriously this is not really a good idea if you are trying to be cheaper. IF you are trying to learn something about speed controllers do it. But if you are taking the chips current rating at its chip value lets have a look at the 85A controllers you have. It uses 3 x 4833N FETs which are rated at 191A each. So if you are going to achieve that from 2A drivers... you are going to need lots of chips. The rated values don't take into account many things, such as thermal dissipation so aren't real world ratings nor are they combat ratings.

IMO that 8A controller there would be struggling to deal with 1000rpm motors in a beetle.

ESC design is an art, thats why I just bypass that phase all together.

Steve

[archie2000]

thanks for all that information
I have a dilema situation.
I am looking at GR-02s for a drive system but don't know which would be better.
12v GR-02 on 14.4v= 86.4stall current.
12v GR-02 on 18.5v= 110 A stall
18v GR-02 on 22.2v= 75.7 A stall

they will be used with an rc heatsink fan to improve efficiency of the ESCs and the motor
thanks
archie

[Ellis]

I'd just run them at their nominal voltage, so 3s for the 12v ones and 5s for the 18v ones. The reliability will be greatly reduced if you try and run 12v ones on 5s, that is for sure. You're more than doubling the torque and putting half the RPM again through a gearbox that isn't designed to take it. This is why Tormenta 2 has so many breakages, we're way beyond the manufacturer's spec. Plus any overvolting is likely to (and rightly) make Ewan less interested in trying to help if something blows.

12v on 4s would probably be alright, but again, you will have absolutely ample power if you run them at their nominal voltages, and very respectable speeds if you opt for 24:1 gearboxes rather than 36:1.

Perhaps try to focus less on the details (you will hardly feel the differences in the arena, if at all, is the truth) and focus more on design. Cobalt mk1 was the perfect example of having just two 550 motors outclass most of its often more powerful rivals, and that was down to good design.