Since my Netduino+ has only 2 UARTS and I want to serially connect all the devices via TTL to it, I’m wondering if it’s possible to daisychain the maestro with the Wixel or the RoboClaw, so by using 1 UART I could send serial data to two devices.
As per Maestro specification, daisychain is only possible to be performed on devices that support pololu protocol or something like that. I’m afraid the Wixel does not support such protocol. Right?
I have not looked into the Roboclaw serial protocol too much, but after looking at the datasheet for a little bit it looks like there is a “Packet Serial” mode that will work well for you. In that mode, every Roboclaw command starts with 128 (0x80) and the data bytes of the command are less than 128. Therefore, the Maestro would ignore any Roboclaw commands it receives, and the Roboclaw will probably ignore any Maestro commands it receives. We have not tested this so there could easily be some unforeseen problems.
The Wixel can be programmed to respond to any type of protocol you want. Are you planning on using a specific Wixel app that we provide?
The Wixel has two UARTs, so if you are going to make your own Wixel all you could use that to free up one of your Netduino’s UARTs.
That sounds pretty good to me! Thank you very much for the research.
I bought two wixels and my plan is to plug one of them on my PC and the other in my Netduino+ via TTL and keep both connected via RF. I’m planning to use “Wireless Serial App” in order to easily pass through bytes from my PC to Netduino+. At the end, Netduino will deal with these bytes according to a proprietary protocol (which I’m just defining by myself ).
Well, that could be a really good option but unfortunately it goes against my initial design. Here is what I want to do:
As per what you mentioned, if RoboClaw will ignore Maestro’s packets and viceversa, hence 2 and 3 could be sticked together by using just one Netduino+'s UART. And (again) that makes me really happy…
Oh! I almost forgot to ask the latest question (promise ) and it is about powering issues…
I’m trying to get the most suitable power input for the whole project and to be honest, I’m kinda lost.
We’ll need to add a Rover 5 to the previous equation since I got Roboclaw from your store with the aim of manage it from my Netduino+. So, the connection schematic will be like this:
Netduino+ <–TTL–> RoboClaw <–> Rover 5
After reading Jan’s blog regarding “Understanding battery capacy” y realized that buying a Lead acid battery will be the better (I must say “also cheaper”, though) choice.
How about getting a 6v - 4 Ah? Will it be ok for powering the following?
Rover 5: 5v … 7.5v (2.4 A stall current at 7.2 v) will be powered by Roboclaw
Another option is also geting 6 x AA rechargable batteries 1.2v 3000 mAh (it’s said that there are 4000 mAh versions around there but I’m not so sure) and do the following wiring:
Lead acid battery (6v - 4 Ah):
Roboclaw --> Rover 5 (will get input power from Roboclaw)
AA battery pack (7.2v - 3000 mAh):
Netduino+ --> Wixel (will get input power from Netduino+)
Maestro
Please, let me know your thoughts. I’ll really appreciate it!
Basically you have to connect each device to a power supply that provides a voltage within the allowed range, and each power supply must be able to handle the total current draw from all the devices connected to it.
I’m not sure where you found the 5 V and 7.5 V numbers for the Rover 5, but DC motors can generally be run at higher voltages than what they are rated for if you willing to accept a reduced life time for the motor. Also, the Roboclaw’s PWM speed control can reduce the average voltage that gets applied to the motor.
Another thing you should consider is weight. A 6V 4Ah lead acid battery will probably weigh a few pounds and slow your robot down.
Six NIMH cells only gets a nominal voltage of 7.2 V which is not enough for the Netduino+, so you are going to need at least 7 or 8 cells.
I think what I would do is fill a 8-AA Battery Holder with NIMH AA batteries (for 9.6 V) or just get a 7-cell NIMH battery pack (for 8.4 V). This will be your main power supply that you can connect to the Roboclaw and Netduino+.
I don’t know how much current the Netuduino+'s 5V line can supply, but if it can spare about 50 mA it should be fine for powering the Wixel.
Unless you have special servos, you will need a regulator (or just a separate battery) to produce a voltage around 4.8 to 6 V for them. You should try to find out what voltage range your servos can run at. You could use a Pololu Step-Down Voltage Regulator D15V35F5S3 to produce 5V from your battery pack. That regulator might be a little overkill, but I’m not sure how much current your servos will draw. Alternatively, you could just a 6.0 V 5-cell NiMH battery pack for the servos. This will be much easier to wire as you can just directly plug it into the Maestro, but then it’s another battery pack that you have to keep charged.
The Maestro’s VIN line can either be powered from any of the power sources we have discussed.
Obviously, this is a complicated system we are talking about and there are many different problems that could arise. I recommend building it slowly, adding one component or power source at a time and testing frequently, so you can troubleshoot it more easily when something goes wrong.
).
) and it is about powering issues…