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  1. CharlieGill

    Touch type heart rate monitors? How do they work?

    The finger tip type like the nurse in the doctor's office puts on your finger is optical in nature. The blood capillaries expand with each pulse so if you shine a led through the finger and filter for red on the detector you will see a pulse with each heart beat. Charlie Charlie Gill...
  2. CharlieGill

    Capacitance of a hydraulic capacitor model

    Your hydraulic capacitor model is right on track, I've used the same analogy before. The larger the diameter of your sphere, the more capacitance. The elasticity would be more on the line of the voltage rating. You can demonstrate DC and AC characteristics quite nicely. Draw a big open tank full...
  3. CharlieGill

    Any Options Other Than Limit Switches?

    I hadn't thought of using diodes, but you are right. I always try to do everything in software :-) A DPDT switch, 2 diodes and 2 limit switches will do quite nicely. Simple is better (but software is more fun). Charlie Charlie Gill --www.calibrator.com--
  4. CharlieGill

    Any Options Other Than Limit Switches?

    I did a quick check... Automation Direct DL05 part# D0-05DR, 8 DC IN, 6 Relay OUT, $99. Software is free for a 100 word program which will be plenty for your application. This gives you all the IO you need for (2) limit switches, Operator input switch(es), motor leads, alarm light, etc. Charlie...
  5. CharlieGill

    Any Options Other Than Limit Switches?

    Limit "switches" are the best way to go, although I would try to use inductive proximity switches if possible. Even if the chute is not ferrous metal, you can attach a small metal target to it. An "amp switch" would be expensive and tricky to set up to eliminate false trips. You would also be...
  6. CharlieGill

    High speed switching using reed switches.

    I would suggest an OptoMOS relay. Clare make several. http://www.clare.com/Products/SSR.htm The LCA715 will handle 1.8A with 0.25 ohms RDSon. Being MOS the 1V signal will not be a problem. With a 3 ms Ton/Toff it is marginally fast enough. I'm sure a faster device could be found but I'm at the...
  7. CharlieGill

    STATIPOWER HF Welding supply

    No suggestions, but I don't think 1975 is all that old :-) Charlie Charlie Gill --www.calibrator.com--
  8. CharlieGill

    SM transformer audible noise and structure natural frequency

    The suggestions above are all valid for natural resonance and the normal operation of a switch mode power supply. I noticed that you mentioned "burst operation". This is often associated with a lightly loaded SMPS. The control circuit will switch from continuous (at an ultrasonic or higher...
  9. CharlieGill

    Double signal on an Apollo Flow Batcher??

    He did get fired. He was the son of a regular employee (who was mortified by the experience) but no official report was made. I don't see how a latching relay will help. Either the PLC is telling the batch controller to run or the BC is starting by itself. If your PLC has data logging...
  10. CharlieGill

    Double signal on an Apollo Flow Batcher??

    Well there went all my great ideas :-) Unless the relay is in the PLC and you have a few hundred feet of cable to the BC7, I doubt noise is the culprit. If it is wired that way, I'd move the relay to the BC7 end as noise can rarely energize a coil. Relays are vibration sensitive. Can anything...
  11. CharlieGill

    Double signal on an Apollo Flow Batcher??

    Some of the notes above don't seem to agree with the BC7 data sheet and manual. The 'scaled pulse" is an output from the BC7, not the input to start a batch. You get one pulse per unit of flow. The 'remote start' input should be a dry contact, not 24V, according to the manual. "It is possible...
  12. CharlieGill

    Intrinsically safe for Class 1 Div 1 Group D

    FM 3610 was the standard I always used in the US for designing IS instruments. It contains the curves for Emax vs C, Imax vs L, etc. It also covers spacing requirements and fault analysis. An IS circuit must meet the ignition requirements with one circuit fault (shorted trace, shorted component...
  13. CharlieGill

    operating in 100% RH, non-condensing

    I would think that 100% RH non-condensing would be difficult to maintain. There's bound to be some condensation as you are right at the saturation point. I agree, conformal coating. Charlie
  14. CharlieGill

    Convert to Serial

    There is not 'cable converter' available. The protocol and interfaces are just too different. There may be a serial to IEEE-488 gateway out there but it would need to resort to a proprietary protocol to do the interfacing. If you are just needing to connect IEEE-488 instruments to a PC there...
  15. CharlieGill

    24V DC Votage Detector-Relay

    PhotoMos relays in the AQV family (now made by Panasonic) will operate with 1 ma forward current and can switch 0.5A. You would need to connect a zener in series to set the detection voltage and a current limiting resistor. If you can be a bit more specific, other options might be better. Charlie
  16. CharlieGill

    finding a cheap oscope

    You can get a Tektronix 465 on ebay for under $200. It's a great scope for general use. I carried one for years in the field and now keep one in the shop for general use. Charlie
  17. CharlieGill

    Fiber Optic Perimeter Security Sytems

    Gee Keith, don't be a wet rag. This sounds interesting. It's not clear to me whether the microwave technology is used to detect an intrusion or just relay the detection (by conventional sensors). From my Navy days I know that fire control radar can track pelicans :-) so I assume a millimeter...
  18. CharlieGill

    Romex

    I'm not a real electrician but I know that Romex is a generic term to refer to plastic covered wire. It came from the Rome Wire Company originally and is now a trademark. Although the term is still frequently used in residential wiring, it has no official maning. It would never be referenced in...
  19. CharlieGill

    How to improve the reliability of critical loop wiring?

    You can use the same logic on your output as you are doing on your inputs. You stated that you were using majority voting (2 out of 3) on your input sensing. Assuming 24VDC outputs, you can use simple diode or'ing to any of multiple outputs to energize the motor starter coil (must have a single...
  20. CharlieGill

    MicroLogix 1100 programming question

    RSLogix 500 (with Linx Lite) is free for small projects which may meet your needs. Here is the link http://www.ab.com/programmablecontrol/plc/micrologix/downloads.html You can also download the manual. Charlie

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