Older blog entries for Trilithon (starting at number 7)

I think I will use different motor drivers. I think that the UC3517 will work best as a stepper motor driver in this app. It will deliver about 3-times the current necessary to drive the motors, and has a simple imput logic control.... afterall, I don't want my PIC spending much time controlling motors. After my main processor, I think I will use a Microchip 16F648 to control the UC3517. Using the 648 to control subsystems simplifies things, but could slow them down too, but I doubt there will be a perceptable lag in performance. However, at this stage of development, performance is not an issue. Safety must be the primary attribute, followed by reliability, and then performance. If attribute 1 and 2 cannot be accomplished, #3 is of little importance. But enough of philosophy. The hardware can be accomplished in several ways, but the above shows a simple and totally practical way of achieving what is to be done with this robot. I come up with new tasks for it daily.


I think I have settled on a microcontroller for this first project... a Microchip PIC 16F877. With plenty of I/O and Risc processing, it should be adequate. Also settled on my on-board power supply. I think I will have 12v at 2 amp hours. This isn't a very large robot, so I think it should run for a couple hours with that, but even so, I have plenty of room to triple that.

5 Oct 2006 (updated 5 Oct 2006 at 04:50 UTC) »

programmed a little today... looks easier than it actually is. Sort of repulsive how large it seems, then you realize it is simple. But then you realize it is harder. Then you realize u=it isn't quite that simple. Then you understand that you are talking to a machine that just does what it is told, and then you realize it is all just addition and negetive addition. Low-level languages are all we need, though. High-level languages deprive us of learning our devices. Learn the device, communicate with it, and get it to do what it really can. In this infancy of robotics, we have the chance to expand and glorify this world. We need to do this in order to bring about changes that will affect and shudder the world. We can do this.

My tiny creature now has legs. I built a couple of circuits to drive the motors, but in research believe this can be accomplished with a couple of ICs. I may scrap my drivers, after experimentation, for the lighter and more space-conserving ICs.

Just got my motors mounted, and the tail-wheel. They all turn freely, and it is a great design for a mobile base. I tried stepping the motors a bit, and found they contained plenty of power to move the base on a level surface. I did not incline the plane, though.

I also completed my MCU programmer, now I just need to make a cable for it to interface, and then I can start programming! I have drawn a few flow-charts which are very condensed and I think I know how I shall aproach the mammoth task.

I am building my stepper controllers tomorrow, and think the robot will INITIALLY use steps for navigation, just as an experiment. But that will not be acceptable in the end product.

29 Sep 2006 (updated 29 Sep 2006 at 06:25 UTC) »

I finished my platform today. It is more crude than I had wanted, but better than I expected. It is a simple plywood thing with cutouts for my recessed wheels, which happen to be 3.5" in Diameter. Tomorrow I drill the platform for the tail wheel, and too accept the stepper mounts. Circuit board mounts have not yet been determined, but the battery carrier is also to be mounted after drilling. Rear docking sensor mounts will also be installed.

I think I will complete my peogrammer tomorrow. I would have this evening, had it not been for losing a couple of 3906 signal transistors which I needed. This is no big problem, but wanted to work on some programming tonight. I am using a Pic 16F877 for my primary controller, and a couple of 16x648's as slaves. I think this arrangement will give me all the power I need for this particular robot, and give me ample room to adapt and modify as needs arise.

This is turning into a very challenging and amusing project, and has been amusing so far. lots of details which I love. And it is fascinating how the more I learn of this field, the more questions come up. Having always been a person who likes multi-disciplinary works, this is really my cup of tea.

I am now considering a triangulation method of having the robot locate itself. Using three small RF transmitters. I am sure someone here has tried this before, and I would love to hear your results.


27 Sep 2006 (updated 27 Sep 2006 at 02:46 UTC) »

I am very new to this so please be patient with me. I am pretty familiar with most electronics, and am in the process of designing a robot which will serve a few household funtions.

I am currently building a PIC programmer, a bastardized version of one of Bojan's. I am going to us a 16F877 for my main controller, and one more to control a few peripherals, addressed by the primary controller as master.

This robot is self charging, self righting, and must navigate complex room interiors. This robot also must utilize voice recognition, though it will be limited to very few commands.

For locomotion, I am using 2 small TEAC steppers, which I canabalized from some very archaic floppy drives. I like to do things cheaply. I also like the fact that if one of my brakes fail, my MCU can sense this and revert to motor braking. Safety is job one. This is one of my largest questions, though... what are the disadvantages to these compared to DC's or servos? I am only using them for locomotion, and not braking, which will be handled differently. But are there any advantages to steppers in this application? Since the steppers are driving the wheels directly, the friction environment will negate the advantage of stepping, in my opinion.

All opinions are considered and appreciated. Thanx. Matt

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