Since last week I've been thinking about building my first project: a robotic lawn mower.
I know setting up the perimeter wire and sensors is fairly difficult but it want to take on the challenge.
I've got some concerns considering driving the brushless DC motors.
Also I don't know if I should use any resistors (for the perimeter wire part I know I should).
I have put a picture below of how I think it should be connected:
Thanks for your reply.
What drive could I use? The only driver I've worked with is the L293N, but that is only compatible for up to 12V.
Maybe the A4988 or DRV8833?
Thanks a lot, very helpful!
I'll dig a little deeper into it and come back when I understand it bit better.
Edit:
I've looked into it and I came to the conclusion that a brushless motor would be to expensive (for now) and could give to much noise for the sensors.
I am switching to a brushed motor with brushed motor driver, both motor and driver are cheaper.
The L298N is capable of only 2A in stead of the required 4.4A (on 18V). After a calculation I found that Increasing the voltage to 24V would give me 3.3A on the driver and 6.6A on the W150.
I guess upping the voltage only leads to advantages in this case?
Now I ussume this, I'm planning on using the TB67H420FTG with (I can barely find this driver online):
The L298 is a terrible choice of motor driver for several reasons. That ancient driver drops 2V to over 4V of the motor power supply in the output stage and dissipates the power as waste heat. So your battery dies sooner.
Choose the motor driver based on the stall current of the motor and the motor supply voltage. The stall current can be several times the running current. The stall current will be drawn, briefly, every time that the motor is started. The stall current should be listed in the motor data sheet.
The BTS7960 is NRND (Not Recommended for New Designs) so if you plan to build a lot of these it's not recommended. However, the breakout boards are easy to find, inexpensive, and the chip works pretty well. I have a couple of them in use.
If the BTS7960 is easy to find, inexpensive, the chips is OK and it can handle high current, I supposed it was hard to work with. Why else woud you not recommend it?
Last year I've done a project in school -> making an automatic 'four connect human VS computer' machine, me making the mechanical parts, someone else doing the electronics, and another guy doing the coding.
Other than that I've never had a big project.
Since I'm in my final year in mechanical engineering, the mechanical part shouldn't be such a problem.
That's good to hear. Do you have anyone at school that can mentor you or otherwise help you out with the electrical as well as digital parts? Picking motors and the electronics is not that easy in itself, then you have the programming of the MCU as well, and much more.
None, but I'm shure I'll find my way if I put enough hours into it. I ordered resistor, inductor capacitor etc. kits so I have room for making mistakes and playing around.
Now I understand the 'NRND' afther a google search. I'll order the module and buy a different module whenever I need one for a new project.
Ah, I see. It's a terminology problem. The device itself is fine. NRND is the manufacturer's recommendation that it not be used for new designs because the chip is being obsoleted. It's a warning so anyone who plans on building 100,000 units with that chip won't be caught unaware when they can't order it.
