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  1. EricRICPDAS

    Parallel Mosfets and Heat Sink

    I like Mosfets for less heat dissipation than diodes. I found that when on, they are low resistance in BOTH directions. Even the 'body diode' becomes low resistance. Is it a good assumption that current really divides equally to three parallel low resistance devices? Note Comcokid's finding...
  2. EricRICPDAS

    Guide robot

    This may sound obvious, but how about a leash? If the leash is a chain heavy enough to cause a dependable caternary bend, then it will not be necessary to wait for a pull on the chain to slow down. Just look for the angle of connection to stay within a range. Stop if the leash drops...
  3. EricRICPDAS

    Accelerometer to get Position

    It matters very much how long the integration must run. If it is a few pulses of high acceleration over a long time of low acceleration, that is a problem. Your 12 bits must then capture the high acceleration, but may not do well at the low acceleration. Because the time is long, the...
  4. EricRICPDAS

    Current Loop Monitoring

    A 4th solution. You can use the data acquisition sensor set to read volts. Then put that across the inidcating meter. This way both the meter and the DAS are using the same shunt resistor to detect current. You can get input devices that are isolated and differential for this, such as...
  5. EricRICPDAS

    comms analysis first go

    I think you don't need terminating resistors with only 2 feet of cable. For example, at 115200 baud, I have only needed terminating resistors with 600+ feet of cable. Too many terminating resistors can cut bias voltage to too low a level. Eric R www.icpdas-usa.com
  6. EricRICPDAS

    Are PLCs still relevant?

    There are low cost PLCs now in the $100 range, which is quite relevant. If you want a graphical user interface, you may want to step up from PLCs to PACs (Programmable Automation Controllers). See http://en.wikipedia.org/wiki/Programmable_automation_controller for a good discussion. They...
  7. EricRICPDAS

    Very basic question: How do they stay in orbit?

    Satellites do tend to drift from exactly where you want them to be. Keeping them in place is called Station Keeping. This generally consumes propellant over time. Satellites in geosynchronous orbit that shut down at end of life tend to accumulate over India. This is because of the Himalaya...
  8. EricRICPDAS

    Spin a Propeller - and smile!

    Oops! I meant 1 mA above. Power is 5V * 1 mA = 5 milliwatts
  9. EricRICPDAS

    Spin a Propeller - and smile!

    What surprised me about these Parallax processors is the low power requriements. The smallest uses just 1 milliwatt. I've been looking at the robot hobby and single board computers lately and find there seems to be something at every level, all the way from these microcontrollers to full blown...
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