Search found 546 matches

by jimandy
Thu Apr 16, 2009 11:59 am
Forum: General Discussion
Topic: Need small monitor for TL system
Replies: 12
Views: 2522

Re: Need small monitor for TL system

Thanks Miguel. That would be about the size, but the MacMini does not output NTSC. The camera does not either, it is basically a webcam that hooks directly to firewire. I need a monitor with VGA or better input.
by jimandy
Thu Apr 16, 2009 6:18 am
Forum: General Discussion
Topic: Need small monitor for TL system
Replies: 12
Views: 2522

Need small monitor for TL system

Using a spare Mac Mini running free Gawker time-lapse software and a firewire Orange Micro camera I have assembled a workable, and quite portable, security TL system. The problem is a monitor. Need one to set up the system but it should be small, in the order of a 5 to 7 inch model to maintain porta...
by jimandy
Sat Feb 14, 2009 10:38 am
Forum: General Discussion
Topic: LED Street Lights Unvieled In Silicon Valley
Replies: 15
Views: 3188

Re: LED Street Lights Unvieled In Silicon Valley

Several years ago Birmingham replaced incandescent bulbs in all traffic lights with LEDs. Now I notice a number of the LEDS are dark. I suppose the fix, if/when necessary, is to replace the entire array rather than individual LEDs
by jimandy
Wed Jan 07, 2009 6:56 pm
Forum: General Discussion
Topic: Ultra Violet and Infrared question...
Replies: 10
Views: 2183

As an aside, scorpions fluoresce green. Really bizarre. I bought a UV light to look for the little boogers in my basement.
by jimandy
Mon Dec 22, 2008 2:28 pm
Forum: General Discussion
Topic: Ignition buzz filter
Replies: 8
Views: 2072

Ignition buzz filter

My son has a problem. He has been through two DC-DC converters to power an iPhone that connects to a built in MP3 input jack in his recently purchased Mazda. He is now hearing ignition buzz that used to not be there when he had the old Volvo. (that’s why he bought a second adapter thinking the fir...
by jimandy
Thu Dec 04, 2008 7:25 pm
Forum: General Discussion
Topic: WHITISH COATING ON HANDLES OF NUT DRIVERS IN STORAGE?
Replies: 6
Views: 1703

I can't answer your question but I can tell you that a number of my plastic handle screwdrivers kept stored in a metal toolbox also developed a whitish coating. I figured it must have something to do with humidity.
by jimandy
Wed Dec 03, 2008 6:11 am
Forum: General Discussion
Topic: current mirror circuits
Replies: 4
Views: 1483

Why wouldn't it be so? A current mirror is a circuit technique that can be build with either sex transistors. Yes, I see that now. I was just curious to know why more examples on the web (at least ones I find by Googling) are of the current sinking variety. To put it another way, in circuit design,...
by jimandy
Mon Dec 01, 2008 6:50 pm
Forum: General Discussion
Topic: current mirror circuits
Replies: 4
Views: 1483

current mirror circuits

My favorite technical reference is Horowitz and Hall (second edition), so for those of you who have a copy, look up the current mirror circuits in chapter two. Notice that they are all built around PNP transistors and show them sourcing a load. Now when I Google “current mirrorâ€
by jimandy
Sat Nov 29, 2008 4:54 pm
Forum: General Discussion
Topic: sump pump monitor
Replies: 26
Views: 6706

Unless I've miss-read your description that configuration is a CGFI sensor, not a current sensor. Maybe so, but my objective was met, a way to detect when a device plugged into a wall AC outlet is on or off and to do it without modifying wires between the source and the appliance and, preferably, w...
by jimandy
Fri Nov 28, 2008 6:09 pm
Forum: General Discussion
Topic: Calculate time constant with a CCS
Replies: 20
Views: 5133

Thanks evahle, I have re-sent the PM and look forward to reading your article. The need for the formula was based on my wanting to design a ramp generator around a schmitt trigger using a CMOS inverter, 74c04 or 132 or equivalent. The formula for PPS for this very simple and often published pulse-ge...
by jimandy
Fri Nov 28, 2008 2:26 pm
Forum: General Discussion
Topic: Calculate time constant with a CCS
Replies: 20
Views: 5133

Thanks to all. My mind just couldn't get around the way to do the computation. Now off to the lab to play!
by jimandy
Fri Nov 28, 2008 2:20 pm
Forum: General Discussion
Topic: sump pump monitor
Replies: 26
Views: 6706

Not finding the answer I have been looking for I just built an experimental current sensor with off the shelf items that does not require interrupting a leg of the power source. Ultimately I hope to use it as part of a monitor system the pump in the basement. Although not finished, here’s the basi...
by jimandy
Thu Nov 27, 2008 4:27 pm
Forum: General Discussion
Topic: sump pump monitor
Replies: 26
Views: 6706

OK Robert, you’re saying you have a clamp-on that if clamped around a regular power cord from a plug in 5 amp motor that you would get a reading? Sounds like if the clamp part was lopped off and attached to an opamp with relay and suitable circuitry then spindown could have the monitoring system h...
by jimandy
Thu Nov 27, 2008 4:14 pm
Forum: General Discussion
Topic: Calculate time constant with a CCS
Replies: 20
Views: 5133

For CCS charging - T =C*V/I
So the V in the formula is the voltage sourcing the CSS right? Obviously it is not the voltage coming out of it (sourcing the cap) since that would be increasing linearly over time.
by jimandy
Thu Nov 27, 2008 2:08 pm
Forum: General Discussion
Topic: Calculate time constant with a CCS
Replies: 20
Views: 5133

Calculate time constant with a CCS

I understand that when you charge a capacitor through a resistor the time constant can be calculated with the simple formula t=RC. However, I would think the formula would be more complex if a constant current source (CCS) were substituted for the resistor in such a circuit since the CCS would seem ...