Search found 85 matches

by rstofer
Fri Sep 02, 2005 9:55 pm
Forum: General Discussion
Topic: opto Isolator
Replies: 15
Views: 3449

Re: opto Isolator

In series as you have it drawn.<p>However, as it is drawn, the inputs are all active high. You need to be certain that the driving circuit can source the current and that the resistor is sized for the actual input voltage. In most cases where you pull up, the voltage will never get close to 5V.<p>It...
by rstofer
Thu Sep 01, 2005 2:25 pm
Forum: General Discussion
Topic: PWM motor circuit and diode
Replies: 31
Views: 4976

Re: PWM motor circuit and diode

You might consider the Intelligent Power Switch http://tinyurl.com/b9oom They're a little pricey at $2.52 (Digikey) but all of the MOSFET driving nonsense has been dealt with.<p>You can see other devices in the Automotive section at www.irf.com
by rstofer
Tue Aug 30, 2005 5:02 pm
Forum: General Discussion
Topic: dc motor chassis as ground
Replies: 5
Views: 910

Re: dc motor chassis as ground

Why not? The starter motor in you can works the same way.<p>Now, I am assuming this is a LOW VOLTAGE motor. All bets are off if the thing is running at hundreds of volts.<p>12V or so should be fine.
by rstofer
Mon Aug 29, 2005 7:55 pm
Forum: General Discussion
Topic: newbi question on relays
Replies: 1
Views: 488

Re: newbi question on relays

Lay it upside down and use small jumpers for all of the pins. Just solder them on and remove them when you are finished.
by rstofer
Mon Aug 29, 2005 6:26 pm
Forum: General Discussion
Topic: EM spectrum and the human body
Replies: 6
Views: 1064

Re: EM spectrum and the human body

There was an interesting graph in the 1994 ARRL Handbook that showed which frequencies were absorbed by the body. YOu might check your local library if you don't have a copy. Other years may be similar.<p>I doubt that it will be all that useful for your project but...<p>Where I worked, we were think...
by rstofer
Fri Aug 26, 2005 8:19 pm
Forum: General Discussion
Topic: pulse width modulation circuit (PWM)
Replies: 10
Views: 1804

Re: pulse width modulation circuit (PWM)

Nobody can tell you that the circuit will work because it depends on the current requirement of the motor. You really have to specify this or everyone is guessing.<p>If you are thinking that you will use a 2N3055 (big TO3 device) because it can handle the current you will be surprised when you look ...
by rstofer
Wed Aug 17, 2005 6:25 pm
Forum: General Discussion
Topic: Senior Design Project (EE+ME)
Replies: 22
Views: 4745

Re: Senior Design Project (EE+ME)

There is a project on the web for a home brew Segway and a unicycle.<p>Start here: http://www.tlb.org/scooter.html
by rstofer
Sun Aug 14, 2005 12:55 am
Forum: General Discussion
Topic: Robot Vision (image recognition)
Replies: 6
Views: 1401

Re: Robot Vision (image recognition)

If you can control the lighting level and the selection of colors, color tracking with the CMU Cam will work quite well.<p>As a matter of fact, the Sumo11 version of the MiniSumo Mark III robot uses Interactive C and there is a library for handling the camera including the chasing of blue or orange ...
by rstofer
Sat Aug 13, 2005 7:06 am
Forum: General Discussion
Topic: RPM display logic check
Replies: 9
Views: 1470

Re: RPM display logic check

I had read the bargraph thing earlier. It would seem that this simplifies the computation in the following way: There are only 20 possible readings between 0 and 6000 RPM or 300 RPM per bar. It should be possible to calculate the time counts that represent the center of each bar and just do a lookup...
by rstofer
Fri Aug 12, 2005 5:08 pm
Forum: General Discussion
Topic: RPM display logic check
Replies: 9
Views: 1470

Re: RPM display logic check

Actually, this is a very nice solution. Then RPM = 1,200,000 / counts between pulses. But it does take a division.<p>Measuring frequency doesn't require a division but it does need pulse rate to get any kind of resolution.
by rstofer
Fri Aug 12, 2005 4:13 pm
Forum: General Discussion
Topic: RPM display logic check
Replies: 9
Views: 1470

Re: RPM display logic check

My guess is that the RPM reading will be VERY sluggish. One of the ways to improve this is to sample 10 times as often and keep a 10 entry moving average. Throw out the oldest reading and keep the latest 9 plus the new reading. Unfortunately, you just don't get enough counts to make any difference.<...
by rstofer
Wed Aug 10, 2005 8:27 pm
Forum: General Discussion
Topic: Measuring analog singal from 0v - Xv where X is unknown
Replies: 11
Views: 1351

Re: Measuring analog singal from 0v - Xv where X is unknown

First off, you can offset and rescale your analog voltages with an Op Amp. If you are only interested in voltages between 11 and 13 volts, simply dividing by 3 to get it in scale wastes a lot of resolution on voltages that don't occur.<p>For a 10 bit converter, if you use the entire 1024 count acros...
by rstofer
Wed Aug 10, 2005 8:16 pm
Forum: General Discussion
Topic: programing FPGA
Replies: 1
Views: 540

Re: programing FPGA

Obviously, there isn't enough detail given to make any solid recommendations but I would start looking over at www.digilentinc.com <p>Their Spartan III Starter Board is quite inexpensive and has a lot of capability. Further, there is a lot of code over at www.opencores.org Pick from what is there an...
by rstofer
Sun Aug 07, 2005 9:25 pm
Forum: General Discussion
Topic: SWM seeks FET for high-powered relationship
Replies: 8
Views: 1528

Re: SWM seeks FET for high-powered relationship

You can also add a 470 ohm pull-up resistor on the gate of the IRL540N. This will help guarantee a rapid transition to full turn-on.<p>Connect the other end of the resistor to +5V.<p>This will add 10 mA of sinking current to the PIC but that is well within the pin capability.
by rstofer
Sun Aug 07, 2005 2:13 pm
Forum: General Discussion
Topic: SWM seeks FET for high-powered relationship
Replies: 8
Views: 1528

Re: SWM seeks FET for high-powered relationship

Save yourself a lot of effort. Use the IRL540N from glitchbusters. It is good for 36A at 100V. But the part you care about is the fact that is is logic level triggered. You can hook it up just the way you said and it will work fine. You may need a heatsink. <p>Connect one side of your load to +12V. ...