Older blog entries for Jimm (starting at number 3)

Boy, it has been a long time since i was here. most of my projects have also been put on hold, but i am hoping to get more time to play soon. Work has kept me busy with projects. Among the things i have completed recently are a 8 channel strain gage amplifier, fixing a S-100 Fanuc robot, and teaching electronics and machining to students. Some of the items of interest i am working on now at the college is a distiller (for water only of course), and a rotary air valve for a robotic are we are developing. the swith itself is interesting. It is supposed to allow a 50/50 air flow split between the output to the pneumatic piston and the exhaust. the purpose of this is to simulate the twitching of your arm when you hold something heavy. i considered using a standard electronics air valve, but the response time was to slow. Plus the rotary valve, since it is motor driven, allows near infinite frequency choices for the arms movement. I will post some pictures of the arm and associated set-up once it is completed. But it will be a while, since I have to machine the whole thing out of 6061 aluminum.

Well last weekend i finished up a little project using a few photo-resistors and two four transistors in two darlington pairs. The result was a simple circuit that changed motor direction by light levels. It worked fairly well on a nine volt battery and would avoid the shadows cast by an object and the object itsef, but a problem developed in the power dropped across the power switchimg transitor and the unit would over heat and until the components cooled down only one turning direction would work.

This cicuit was really just a study in designing one "nerve" for the main robot design, but it told me alot about imporvements to do to increase the sensitivity of the cells and response time. I know that there are many other IC units that can be used in place of transistors, but I really like the durability and recovery properties of transitors. IC's are great but they have a great limitation when exsposed to high heat or electromagnetic interferance.

Some of the systems I worked on in the Navy really took this lesson home. The main room all of our equipment needed quite a large AC system. If it ever went out the bays would get hot enough to give you a good burn. After the heat went down, the only equipment to survive without great need for repairs, was the stuff built off of old 1960's and 70's designs. Everything using mostly IC circuitry would be dead or near dying. Course, not that I don't love IC's, I just think we shouldn't depend upon them for all applications, same with transistors and such.

I had another thought today,(I really should be carefull), and that was what if for obstacle detection and sensor input you used three input devices (you pick) then ran the inputs into a comparator circuit. The output of the comparator would then be sent to the CPU or controller device. Statistically this should inhibit the chances of random noises or light from confusing our mechanical friends. Especially if you used three or more inputs and offset the level that the sensors were lined up on. Example use an isocolese (I know that is spelled wrong, but hey it's public education for you!) triangle or hex patern. If you got any thoughts on if this would be a feasible alternative to more exspensive sensors and detection systems... please let me know. jaltop@stmartin.edu

sin jimm

Just a thought: one of the problems i see with reducing the weight of the robots power system is that there needs to be enough electrically energy to power and sustain the unit for x amount of time. this ussually involves one large battery or several small ones. the weight of this adds together and requires the drive motors to need more torque to move the heavier system containing all those batteries. But what if you were to use two rechargable batteries and a solar collector, a few relays and possible a comparator or time to do this: have one battery just large enough to supply the motors with enough energy for movement for x amount of time. the second battery will be charged by the soloar cell for y amount of time. When the first battery is low, a comparator, timer or relay will actuate and switch the system to the second battery which should by now be charged. The same switching then transfers the charging process to the first battery, while the robot continues on with objective. i see a few bugs in this system myself right now, but any thoughts you mighthave....

sin jimm

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