MadeUSA Construction/WIring Questions
I just received the parts for the MadeUSA robot and had some simple questions before going too far...
P.S. I also had problems getting the pins into the axles -- it took a fair amount of patience and time to get these in, and I sincerely hope I won't need to remove them!
- The LED extender tubes that came with the Ultrasonic mounting brackets do not fit the brackets (hole is too small) -- it would appear that the holes need to be drilled larger. Anyone else run into this problem?
- The two denso motors come with an automotive-like large plastic connector at the end of the connection wires -- apparently that needs to be cut off to expose the yellow and black wires, nright? Also, there is either a fuse or connector of some sort inline on the blue wire -- anyone know what this is?
- Mounting of the robot controller (Propeller): Is there a resource for hardware needed to mount this on the MadeUSA base?
- Battery connections: What would be an appropriate power switch/breaker and cable size, given a PB-1070 (12VDC, 7Ah) battery, a Propeller robot controller and the base parts of the MadeUSA kit? i.e. how much current should I allow for in this configuration? With future, larger power needs, what is a reasonable maximum given this particular battery?
- Is anyone aware of an easy way to provide a jack for charging the battery which would automatically disconnect the batter from the robot when plugged in? I'd like to avoid having to disconnect the battery from the robot each time it needs charging.
P.S. I also had problems getting the pins into the axles -- it took a fair amount of patience and time to get these in, and I sincerely hope I won't need to remove them!
Comments
Sorry you're having troubles...let's see what we can do-
The "light pipe" (as we call it) may have a "mushroomed" end, or a "normal end". The tolerance is very tight, but you should be able to friction fit it through the hole. Once in, it shouldn't slide out. If it still doesn't quite fit through the hole, use some fine sandpaper and taper the end a little bit to get it started. If you're still not getting it to fit, call Tech Support and ask for either Dave or Nick - they'll get you goin'!
Yes, you can cut off the wires to the appropriate length required for you application. In my case, I decided to cut them quite short, and connect them directly to the HB25's. I like to keep the leads as short as possible (to minimize voltage drop). There is no fuse in the wires, just splice blocks and/or terminals.
Although we like Stamp's and Propeller's (duh!), Madeusa can be controlled by any microcontroller you prefer. As far as mounting a controller to the platform, there is a short discussion (in the documentation) on how to drill pilot holes and then use standard machine screws and spacers to mount the board. I have a Board of Education mounted on mine right now, and I've connected the HB25's to the servo headers on the Board via (3) wire standard servo connectors.
I would use a switch rated for at least 10 amps (the two motors can easily draw 2 amps or more by themselves - plus everything else, plus extra margin). Automotive switches work really well, and are routinely rated for 12v at 15A or 20A. Some are even lighted (although I tend to not want to draw any "non-essential" power as much as possible). And yes, adding a fuse block or circuit breaker is good design practice -
The Battery Shelf is designed for a 12v 7.5Ah SLA battery. That should provide multiple hours of operation between charges. Also, we're currently testing a "double-sized" Battery Shelf which would provide double the run-time. That is, 12v @ 15Ah.
Madeusa is a work in progress, and you've hit on one of the circuits I've got on my design desk right now. While it's not yet available, that's one of the projects that I'm currently working on. The easiest way to charge a battery of this type (for now) is to use any of the commercially available chargers out there, or alternatively, build a simple circuit based on the PB137 SLA charger chip. It's a three pin device, and is just about totally "bullet-proof".
Yes, I know - me too! The holes are drilled @.125", specifically for a .125" roll pin. We've recently increased the hole diameter to .128", to allow for a more easily inserted pin. (A .125" roll pin is considerably bigger than .125" in diameter, and the fact that it's steel and the axel is aluminum, makes for a very snug fit.
Hopefully, you'll never need to remove them, but in the unlikely event that you do, there is a simple solution: Support the assembly so that you can pound the pin so that it is flush with one side of the hole. Then using an appropriately sized "pin punch" (automotive supply stores typically carry these), drive it all the way through, and out. I've done it. Not a "cake-walk", but very doable.
Build your robot, take pictures and post your experiences and results here on the Forums!
Per your recommendation, I was able to sand the light pipes using some fine sandpaper which allowed me to push them through the holes in the Ultrasonic mounts just fine. I used the flat side of a wire cutter to push gently until it was the proper distance from the PCB.
As for the robot controller, I got the $99 Propeller Robot Controller which I believe was recommended at the time -- it is now discontinued! I assume the two motor ports on that board can be used for other motors (robot manipulator/arm?) in the future, as both HB-25's appear to be controllable with a single I/O port (one of the 24 on this board). I am curious about the fact that this board does not seem to make the video capabilities of the propeller available as other Propeller boards do, but I'm not sure what they would be used for on the robot anyways unless you're into watching "motion" pictures. ;-)
The battery shelf's additional holes allowed me to use the recommended battery (PB-1070, 7Ah) with the provided metal spacers -- the battery fits snug and only requires two spacers to be removed to remove the battery, which fits perfectly vertically between the robot base and the battery shelf. I purchased the battery from Mouser as recommended, along with a matching charger (Mouser p/n PSC-12800A-C, 12V 4-8AH 800mA).
A charging circuit would be a nice upgrade/addition for the Madeusa down the road. For now I'm thinking of using a DPDT switch (sufficiently rated per Matt's recommendation) to switch the battery between charger and robot, or perhaps just an SPDT with a common ground.
I don't have much more to share for now, other than the wife not liking the HDPE (black) smell too much! :-)
The odor is from the butadiene rubber in the tires. The HDPE should have no smell unless it's burning!
There *could* be a slight odor caused by the carbon black (that's what gives the plastic its black color), but I think you'd have to lick it to taste it!
-- Gordon
Back to wiring issues. I've been searching around for a fuse block or better yet a circuit breaker block with 4-8 circuits to protect the various components on the robot, along with a master breaker/power switch. I am trying to plan for future expansion. The only thing I've found so far is Digikey p/n 3539K-ND (a 4 fuse holder).
Does anyone have any recommendations?
The rest of my system is powered by Matt's li-poly pack/charger, and it has its own 2A mini blade fuse that will trip if there's a short anywhere in the electronics. A second, smaller, switch controls the power from the li-poly pack to the electronics. I didn't want to run the power from both the battery and li-poly through the same switch in case of mechanical damage to the switch and the two circuits fusing together.
I suppose separate fuses for subsystems could be added, but on a robot like this would they be necessary? They do it this way in cars so that faults are isolated, enabling you to keep driving. Not sure if that's super-critical with a research robot like Madeusa. What I'm finding is available space is going fast. I'm putting mine on a diet to conserve real estate.
-- Gordon
I'm looking forward to having a drivable robot!