I'm starting a new robot project that will utilize an RC truck chassis and it's DC motor and drive train. This is a four wheel drive chassis turning some heavy rubber tires and it is expected it will be drawing a lot of current. I'll share the stall current as soon as the battery pack charges up and I can test it. It uses a battery pack that is 6 nickel cadmium cells and I believe it's a 2200mAh pack. The truck when it was an RC vehicle typically depleted the battery in around ten minutes. I'll be powering the Arduino, any sensors and servos with a separate power source of four rechargable AA batteries so the battery pack will be dedicated to only the motor.
I will not be using any motor shields for this project but I'm not opposed to transistors or relays. I would prefer to use a dual H-bridge so I can control speed and direction. From what I'm reading it sounds like the L298N is a good candidate, I'm just wondering if there's a better option.
The L298N supports max. 2.5A (each channel) in PWM mode. The total drop of up to 4.9V@2A (+current sense) looks quite high, for 6 NiCd cells (9V?). But you don't want to build a racing robot, I assume?
Don't you have left the original motor driver electronic?
Why not a shield? You will always need a PCB to hold the transistors and relays.
Speed and direction? Is it skid steer like a tank or does it have steerable wheels?
2200mAh in 10 min seems like 15A average load and the peaks are going to be at least double that. My first recommendation is the Sparkfun Monster Motor Shield but even that may be underpowered here.
I do still have the original components that handled speed control. Unfortunately this was a RadioShack RC truck so all of the controls is a sloppy board covered in transistors. It's not usable. As for motor shields, well, I have to drive a servo too so that's not going to work thanks to servo.h disabling PWMs. It's more interesting to build a motor driver than to try and re-write somebody else's bad code.
As for the speed and direction question, the vehicle has four steerable wheels. And a four wheel drive gearbox and differentials. I've already torn the chassis down and replaced the steering servo which had six wires with a real servo that has three. It also happens to be a metal gear servo.
I forgot to put a battery on the charger last night but was able to do some testing with a mostly charged pack. At power on the motor spikes to 8.5 or so amps and drops down to 1.5, that's without the wheels on. These wheels weigh at least a quarter of a pound each.
I've got an idea and I want to know what you guys think. What if I only need to go forward? Could I use a power mosfet and PWM from my Arduino to control motor speed? I've got a bin of various button transistors and there's some 40watt mosfets in there. Just wondering if one of those might be usable.
Two more hours until the battery pack is charged and I'll get the stall current.
Okay so it looks like the maximum current draw is around 14.5 amps. these are short spikes like when the motor is trying to initially spin up the four wheels, stall current is around 8 amps and running current with the chassis turned upside down and the wheels free-spinning varies from 1.8 to 2.8 amps.
I'm concerned that if I change out this unknown motor for the Astroflight hobby motor I was planning to use, these numbers may go up even more. So for now I'll just keep the cheap motor in there.
I've got a maker group meeting this afternoon so I'll interface with those guys and check back here tonight or tomorrow morning.
funny I've never seen an Arduino product from China that wasn't a counterfeit. I'm not saying these are but the price and the country of origin suggests they might be. These do seem to be right in the ballpark of what I'm looking for though. I'll have to check more into these.
funny I've never seen an Arduino product from China that wasn't a counterfeit. I'm not saying these are but the price and the country of origin suggests they might be.
??? This H-bridge is a counterfeit version of what? Do you have a link to the non counterfeit H-bridge?
I'm saying it's likely a counterfeit because they're using the Arduino logo without permission, as a lot of Chinese manufacturers do. They put the logo on their products so people assume it's made by this company and thus is 100% compatible.
It probably is compatible and works just fine, but using the Arduino logo without the consent of the company is improperly implying affiliation with that company.
raschemmel:
I don't think there is a Genuine BTS7960B 43A H- bridge driver so I guess that must be a fake Arduiino Product.
That's all I was saying. It's an unauthorized use of the company's name and trademark logo. I'm sure their products work great, aside from their huge disrespect to Arduino.
Well that's not exactly true not is it ?
It is well known that "imitation is the highest form of praise".
They wouldn't be using the arduino logo (illegally) if they didn't have the highest respect for it's reputation.
The "knock-off" black market has always targeted the most well known and popular brands. (like Gucci, Levi, etc) What you should be asking yourself is "why is there no Genuine BTS7960B 43A H- bridge driver ?"
The fact that there is a "knock-off" of a non-existant Arduino product should raise questions .
