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    Need help with a brushless motor?

    You need to drill down and search into the CD-ROM motor rebuild links. There is a whole community of RC plane makers who build CD-ROM foamies and wire their own motors. http://goldeneye.ethz.ch/motoren/electric/cdrom/index_EN http://www.flyelectric.ukgateway.net/cdrom.htm Commercial...
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    Where to find strain gauges

    A quick scan of this site shows a ten pack starts around $49 dollars http://www.omega.com/toc_asp/subsectionSC.asp?subsection=E02&book=Pressure Try Trossen Robotics if a flexible force sensor of some sort might also do for your needs.
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    Replacing a Wall Wart Power Supply

    The concept I tried to describe relates to turn-on transient conditions. This pdf is a checklist for switching power supply specification including the term "turn-on delay." http://www.umecintl.com/pdffiles/lcd/UP1232A-01.pdf This link has a 138 page pdf by On Semiconductor regarding...
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    The significance of material science and technology

    Ask the professor for a course syllabus. I took basic materials science (mostly an introduction to metalurgy) and semiconductor devices (quantum electronics, field and waves, and material science). Both courses have proven useful in my work as an engineer and patent expert. Find the professor...
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    Replacing a Wall Wart Power Supply

    This reference may be a bit overkill. The output of a switch-mode power supply includes inductors and capacitors which must absorb energy at turn-on, if I recall, it takes cycles of AC power to charge up the components and this would influence setup time: http://www.smps.us/topologies.html...
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    Choosing the right micro controller

    This developer sells 14, 18, 28, and 40 pin PIC parts with a simplified instruction language, communication tools, and custom commands pre-installed. You pay a little more for each chip and need a USB to serial port converter cable, but it could cut your development time significantly depending...
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    Power Required to Drive Large Flywheel

    Does this differential equation for the mechanical system offer you some insight? I use it to study the spin-up characteristics of tiny permantent magnet motors. The principles are the same but the actual model you use may need some refinements: T_{IN} = J_{EQ}\frac{d \omega}{dt} + D\omega +...
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    Making RC Controlled Objects

    You might be best off trying to hack an existing IR tx/rx from an inexpensive toy: http://dealspl.us/product/new-super-wall-climber-remote-control-mini-car-w-infrared-controller [Broken]
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    Calculating Size of Resistor needed?

    I decided to try 5Spice and ran this saturation model of the TIP41C with success. A load resistor RLoad = 24 ohms will draw 0.500 amps at 12V, so I put this in as the coil resistance. R1 = 330 ohm 0.5 watt rating 5% tolerance. R2 = 3.3k ohm 0.25 watt rating 5% tolerance. Base current is...
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    Calculating Size of Resistor needed?

    Sorry I forgot you're not EE so my instructions did not explain how to find the voltage across each component. But you have the right idea. Instead of building and testing the circuit (or before doing so) you could build it in a free student version of SPICE. Depends on whether you want to...
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    Calculating Size of Resistor needed?

    So far you're on track. I would insert three R1's and three R2's, one for each transistor, and run two of the R1 inputs to a single push button switch input. This might even make the board layout simpler. Your design might work as is, but I haven't thought about it. Direct current power...
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    Calculating Size of Resistor needed?

    The link I inserted above mentions the 1N4001 which used to be available at Radio Shack. It can flow 1A and has reverse breakdown 50V. http://www.fairchildsemi.com/ds/1N%2F1N4001.pdf [Broken] The 1N4002 has 100V reverse breakdown, and so on. I don't know how much inductive voltage spike...
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    Calculating Size of Resistor needed?

    In the attached circuit you calculate R1 to saturate the NPN transistor when the switch is closed. You set R2 = 10*R1 approximately to ground the transistor base when the switch is open and ensure the transistor turns completely off. I would run two solenoid drivers in parallel from one push...
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    Need a mecanical generator for experimentation.

    The stepper motor is a good idea but a small DC permanent magnet motor is a simple machine to do some preliminary experiments. You can get them out of old toys or stuff around the house, or buy them pretty cheap too. You can turn it with a variable speed drill and note the voltage increase at...
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    Monitoring a Live, 80W, 12VDC Load

    Digikey sells Allegro current sensors. You can keyword search for In Stock parts. This product can sense 20A but operates off of 5V, has linear output, and is surface mount: http://www.allegromicro.com/en/Products/Part_Numbers/0713/0713.pdf So you'd need to do some work to make it work...
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    Calculating Size of Resistor needed?

    Have a good trip home. This page gives the bias circuited needed to use the TIP41 transistor as a low side switch (but the size of the flywheel diode is still uncertain): http://www.rason.org/Projects/transwit/transwit.htm We can go through the design, build, and test procedure when you're...
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    Calculating Size of Resistor needed?

    This is an obsolete part but you'll get an idea of how you would use it. Datasheet for a high current high side switch: http://cds.linear.com/docs/Datasheet/1089fa.pdf [Broken] My sketch is a low side bipolar transistor switch and yours is a highside FET switch. It would be good if you can...
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    Calculating Size of Resistor needed?

    The second pdf offers an option to purchase with the surge suppression diode. I suggest purchasing with this option unless you plan to choose your own suppression diode: 17N = DC Solenoid W/Surge Supression Diode See if such an option is available for the other solenoid model, and try to...
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    Need help modifying rc car circuit

    google key fob reciever. There may be an economical solution already available. http://www.homesecuritystore.com/c-121-keyfobs.aspx Good luck!
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    Need help modifying rc car circuit

    Most older RC receivers need more than 4.5 volts to operate as far as I know. It may be hard to eliminate voltage cells on the receiver. A step up switching power supply is a solution but hard to build yourself and probably costly to purchase. You might try to google for Rx hack that works on...
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    Calculating Size of Resistor needed?

    The attached gif (left side) is taken from this page on robot solenoid: http://robots.freehostia.com/Solenoids/SolenoidsBody.html You want to use the NPN transitor as a "low side switch" as shown on the right. The transistor should be fully on (saturated) when the pushbutton closes. Notice...
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    Calculating Size of Resistor needed?

    You've asked a simple question, but the design may call for a bit more complication. For example google the term "solenoid driver" and look for some images. The driver depends on the solenoid properties and application requirements. Are the solenoids to be operated momentarily or latched? If...
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    Calculating Size of Resistor needed?

    What current must flow in the solenoids? If you have a spec for these components please post. I don't think I_B = 3A is the relevant parameter, but I need to understand the load to consider how the transistors will work.
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