Robotics

This board is designed specifically to control the 5-motor Robot Arm sold by Baycom Technologies. It has no input facilities, but it is less expensive than combining the I/O Board with the Relay sub-Board. If you need lots of relays and no input, this is the way to go.

An opto-interrupter made with Lego beams, regular parts, a 6 hole pulley wheel and an axle.

Occasionally, a system needs several digitally programmable voltage-output channels. Such output channels typically provide the control for robot positioning, industrial processes, and even home automation.

With a handful of inexpensive components, a little creativity, and the power of PicBasic, you can build some pretty outstanding robotics creations as Rob Arnold proves with his Ruf-Bot project. RF remote control is just way too cool not to use in your designs, but if you're a newbie like me it's difficult to successfully build solid RF transmitters and receivers on your own. When I started out I didn't realize that the larger breadboard I was working off of was causing a lot of the signal deviance because the metal traces on the breadboard worked like small capacitors, and changed my circuit dynamics.

The 1381 solar engine uses a 1381* voltage detector (a.k.a., a voltage supervisor) IC to drive a voltage-based (type 1) solar engine. The 1381 is normally used to reset CPUs and Micros when the power supply drops too low for reliable operation. So 1381s detect and switch when the input voltage crosses the rated upper and lower threshold voltages. The upper- and lower-switching voltages are slightly overlapped so that the turn-on voltage is a few hundred mV above the turn-off voltage.

eve Bolt came up with an interesting 4-transistor H-bridge variant; this is cheap and easy to build, and best of all is "smokeless" (i.e., no combination of inputs can cause the bridge to self-destruct). Here's Steve's diagram:

In March of 2003, Manfred Schaffran posted a solar engine design using a 555 timer IC: Wilf Rigter simplified this circuit a bit, made it phototropic, and doubled it up to yield a photopopper design in a post later the same day. I've got this design written up elsewhere in the library.

This is the six transistor "Tilden style" H-bridge; while not as old as the original "basic H-bridge," this goes "way back," and is the basis for many BEAM driver circuits

The Atmel AVR series are very good microcontrollers with quite a rich instruction set, rich enough that lots of folks have good compilers for them so we don't have to learn their assembler. A very rich compiler available is the BASCOM/AVR compiler from MCS Electronics. I've used this compiler for prototyping the software on my 90S2313 robot board for two reasons: One, It has a very rich command syntax; Two, its free in its demo version! The demo version only supports 2K of instruction memory, other than that it is completely uncrippled.

I volunteered to turn a friend of mine's Warhammer 40K Imperial Rhino personel carrier into a remote controlled item. Little did I understand the undertaking that I had agreed on! My requirements for this project were that the transmitter and receiver had to be a single chip design, done all in software. I succeeded. The receiver chip uses a Panasonic 4602 38KHz receiver and that's it for external components. It has the serial input (GP3) , two RC hobby servo outputs (GP0/GP1) and three digital outputs (GP2,4,5). Here is the code for the receiver chip.

This Robot is still being constucted so if you have any ideas please send them to me. I would apreciate if those people who keep sending me e-mails for me to send you my project schematics, look at the "Schematics page" located to your left on the menu. I dont have anymore schematics for the time being.Also is there anybody who knows how to controll a servo?

A simple test circuit allows you to make these measurements (Figure 1). The basic idea is to create an oscillator by feeding an output signal back to the control input and then monitor the control input with an oscilloscope. Then, you can easily monitor the upper and lower transition points on the scope. To slow the frequency of oscillation and reduce the effects of propagation delay, it’s sometimes desirable to add an RC network.

The 74AC240 stepper driver works by alternately enabling each half of the buffer. Only one half can be enabled at a time. Let's assume that the top half of the driver is enabled. U1A & U1B along with R8, C1, and the input protection resistor R7 form a square wave oscillator. The outputs of U1A & U1B directly drive one coil of a bipolar stepper motor.

The LDR's were hand-picked. Got two packages of them from Radio Shack, looking for at least two pairs of similar parts. Then added wire-wrap pin sockets, to the circuit, so that the LDR's could be plugged in. Currently, the 0.33UF cap is not being used on my B-Head's. I made a long J-hook from "Jumbo Paper Clips", attached it to the motor shaft, and then hung it from my rear-view mirror so it can "see the lights". <grin> (Pix below)

The MiniBoard, a Motorola 68HC11 Robot Controller board designed by Fred G. Martin, also uses this driver. The day after, I then decided to prepare the page describing how to use C-52 EVB as a robot controller board. I asked my student for competition, build yourselves robot that can track the black tape. Prize for the winner is 100 US$, with a bit condition that the winner must pay for a big party at Soi Jinda's Somtum (Papaya Salad) shop. And one of the competitor is me. I thought the rule should be conceived roughly by students and technically by me. The picture on that day will put here soon.

Craig Maynard dreamed up the Chloroplast solar engine (an interesting design, tho' it uses two parts you probably won't have sitting around in your parts drawer). Since I really can't describe it better than Craig can, here's his description (from the Chloroplast web site), followed up by commentary and a related circuit by Wilf Rigter:

Intelligently modifying the motor-drive commands to a robot can give you control finesse during competitions. Moving a joystick hard right, for example, might have different effects, depending on the robot's speed and direction. Software running on an inexpensive microcontroller (in this case, an NEC (www.nec.com) PD78F9814) manages this control by calculating separate drive and adjust vectors and then combining the vectors and calculating the appropriate power ratio for two tread motors (Figure 1). This demonstration system uses a simple treaded toy vehicle to show how the ratio-drive concept works and requires no sensors in the vehicle.

The design is simple, tuneable, but no longer terribly useful (I include it here just for purposes of education and folks' historical interest). This design has a number of weaknesses; courtesy of Wilf Rigter, here are a few:

A very popular circuit for driving DC motors (ordinary or gearhead) is called an H-bridge. It's called that because it looks like the capital letter 'H' on classic schematics. The great ability of an H-bridge circuit is that the motor can be driven forward or backward at any speed, optionally using a completely independent power source.

The dual slope-sampling solar engine. Yet another interesting design from the fertile mind of Wilf Rigter If you had time to experiment with the ALF type SE circuit you may have discovered some of its shortcomings with regard to a Power Smart Head adaptation. The problem is that HCMOS gates are power hungry when used as SE voltage comparators when the analog input voltage is near the CMOS switching threshold. If an HCMOS gate is used without sampling, the chip supply current can be as high as 70mA with the comparator input voltage near the trigger threshold (Vcc / 2).