Propeller Controller Cards

Propeller Cards

I have been using the propeller microcontroller chip for robots for about three years now. There are pros and cons to using this particular chip, but assuming you want to use the that chip, what is the best board for robots?

Propeller Proto Board (no USB)

Since it was probably the first board available, it's no surprise that the first board I used was the Propeller Proto Board.

Pros

This board is really inexpensive now, particularly if you get the one with no USB connector built in.

It has the wiring for four servo connectors on the board. You have to pay a little extra for the hardware and solder it on yourself. You can also add a variety of connectors in the prototyping area. There is also a plug for a wall transformer so that you can power the board from an outlet. That's really only useful for testing.

Cons

While this board does have a plug for a transformer, it does not have plugs for or terminals for a battery. You can solder them on, but you have to do it yourself.

The four servo plugs that are laid out on the board require some additional hardware and soldering. If you want to add more than four servo plugs you will have to wire the plugs in the prototyping area. The servo leads do not usually have a pull up circuit so the signals to the servos will be 3.3v. In my experience that isn't usually a problem.

Since this board doesn't have a USB connector you need to buy a Prop Plug in order to program the board. You can share one Prop Plug across a variety of boards. In my experience Prop Plugs do eventually break from wear. I believe I am on my third in as many years. But I use the plug a lot on a variety of robots. Robots are particularly hard application for any sort of tether or plug because they can always move or jerk unexpectedly.

Spin Studio

The next board I started to use was the Spin Studio. I used it on Fluffy and Sterylite 6000. This board was the first propeller board with modular expansions.

Unlike the propeller proto board you have to solder the whole thing together from parts yourself.

Pros

Since you solder this board together yourself it is easy to substitute a battery plug for the transformer plug.

There are a number of expansion boards that are useful for robots. There is a servo controller board and an XBee wireless controller board. There are boards for a variety of input and output devices, as well as a prototyping board. Another nice feature of expansion boards is that you can swap them out. So you could put a TV board in to aid debugging and then replace it with a servo board when the robot is in operation. Swapping expansion boards also lets you try different configurations and reuse components.

Cons

The biggest problem with the Spin Studio cards is that they are really big. You can see it takes up almost all of Fluffy, a pretty big robot. The size was fine for a robot the size of Sterylite 6000, but would have been a big problem for a robot the size of the Peanut Tin of Terror. I like this board but I really want to use something smaller.

You have to hand solder everyone you use, which can get a little tiresome.

Propeller Robot Control Board

I was very excited when this board came out, because it was the first propeller board designed for Robots. I have gotten two of them, and I still use on the Peanut Tin of Terror.

Pros

This board is very well setup for servo controls. There three banks of eight servo plugs, for a total of twenty four plugs. Each of the three banks can be set to the voltage coming into the robot or to an adjusted five volts. Having different banks set up like that is great because it means you can drive some plugs a 5v, others at 7.4v, 9.6v or whatever.

The servo pins all have voltage level translator circuits so that the signal to the servo can 5v instead of the 3.3v that is typical of the propeller chip. Better still, you can bypass the circuit with some soldering if you want to access the propeller pin directly.

The board also comes with two h-bridge circuits to drive DC motors. H-bridges aren't my favorite way to control a DC motor because you don't have as much control over the speed as you can get with an electronic speed controller. But by turning the motors on and off rapidly you can get a variety of speeds and you can go backward and forewords.

The board has a plug for a transformer and plugs for wires to a battery and to two drive motors controller by the H-bridge circuit.

Cons

While there are plugs for batteries and for the motors, I really do not like the plug format. You can get plugs to use with this board from Mouser electronics. They have never really worked that well for me. I often have had trouble getting a connection that is durable enough to withstand the stresses of impacts.

This board is also on the expensive side. At $99 its the most expensive board of the group. In general I think I can get the same (less the H-bridge) with a cheaper board. Since I am not really interested in DC motor control I don't really need it.

Sometimes the voltage translator circuit seems to interfere with certain types of circuits, like serial io. In that case you have to bypass the servo pins to get access to the pins on the propeller.

Propeller Servo Controller

The Propeller Servo Controller is a replacement for Parallax's previous servo controller that used to have another chip. The card is marketed as a way to control servos via a USB. But guess what? It is completely reprogram able and you can use it as the board on your robot, as I do on Kudu.

Pros

It's pretty cheap at $39.99. It's pretty small.

Cons

Only sixteen of the propellers pins are easily exposed by servo headers. All of the exposed pins have voltage translators, so it is difficult to integrate this board with some sensors. And you just can't get to a lot of the io pins since you are limited to p0-p15.

Propeller Platform Kit

Gadget Gangster makes the Propeller Platform Kit and the Propeller Platform USB which is not a kit. This is a newer Propeller board that is really promoted by Parallax. There are many modular board kits that plug on top of the platform to customize the board.

Pros

This board has most of the benefit of the Spin Studio since you can expand it. It's better then the Spin Studio because:

It's smaller.
It can be gotten as a kit or pre-assembled.
It can be powered by a transformer plug or by batteries connected via screw terminals.

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Propeller Cards

Propeller Proto Board (no USB)

Spin Studio

Propeller Robot Control Board

Propeller Servo Controller

Propeller Platform Kit