Search results

Search Forums New Posts
  1. hevans1944

    I need a detailed Analysis on this circuit

    What!? You have never received an e-mail from a Prince in Nigeria offering to share his fortune with you? You only have to send him a good-faith deposit to secure the balance of $_________ (fill in the blank) yada, yada, yada... I am not sure what the scam here involves, but I am pretty sure no...
  2. hevans1944

    BNC connector

    This Wikipedia article says the Passband is typically 0 to 4 GHz. Without a deeper understanding of transmission line theory, the OP might be led to believe that somehow at 4 GHz the BNC connector suddenly stops working. Real world devices almost never suddenly stop working. Degradation in...
  3. hevans1944

    What would be the best soldering iron for $200 and under?

    No, not a change in heater elements. Heater stays the same and you only select one of three temperature-regulating soldering tips to use with the heater. The temperature control is in the tip, by means of a magnetic material whose Curie temperature is the same as the tip temperature: 600 F, 700...
  4. hevans1944

    What would be the best soldering iron for $200 and under?

    Well, since we are in a confessing mood, I will confess to wanting a hot-air work/re-work station for SMD projects. You can easily spend thousands of bux to set one of these up, but judicious purchases of Asian components will get you a decent rig for a couple hundred bux. Of course that does...
  5. hevans1944

    What would be the best soldering iron for $200 and under?

    Depends on the model. Here is a manual with schematic and parts list for the WTCPT model.
  6. hevans1944

    What would be the best soldering iron for $200 and under?

    Are you blaming your Black & Decker soldering station for the cold solder joints on your PCB? What model B&D soldering iron do you have? What temperature does the soldering tip reach and maintain while soldering? Cold solder joints are almost entirely the result of poor soldering technique...
  7. hevans1944

    What vibration sensor for bearing monitoring

    That's okay. I liked your post because of the third link to the Vibration Sensor Catalog. That seemed most relevant to bearing failure testing and a pointer in the right direction, as requested by the OP.
  8. hevans1944

    12VDC Backup supply

    So, are we all done re-inventing LoJack?
  9. hevans1944

    What vibration sensor for bearing monitoring

    Single-axis accelerometers are what we used in our bearing test rigs. Bearing failure, indicated by a sudden increase in vibration amplitude, initiated shutdown of test rig. Most vibration accelerometers use a "proof" mass attached to a piezoelectric crystal to form an accelerometer transducer...
  10. hevans1944

    Trying to get a PIR activation to increment a 7 segment display correctly

    Ah, the "fun" of interfacing high-speed CMOS logic with the real world. I was gonna respond to this thread, but Harald beat me to it with a very good explanation. ALWAYS de-bounce mechanical switch contacts before attempting to use the contacts to create clocking events. There are many ways to...
  11. hevans1944

    Positive Tolerance of PV modules

    I think it must have something to do with marketing. You wouldn't sell a can of beer as being 32 ounces plus or minus one ounce. No, you would make sure that can contained at least 32 ounces. Same-o same-o with solar panel modules. If you advertise your module as producing 300 watts under...
  12. hevans1944

    Progress

    Back in the day... Sams Photofacts folders had excellent schematics that were augmented with notations of voltages and waveforms to expect at various nodes in the circuit. Some even included actual oscilloscope photographs of the expected waveforms. With a decent PDF editor, it should be easy to...
  13. hevans1944

    Strain gauge conditioner/load cell amplifier

    Holy op-amps, Batman! Where did you get your engineering degree? The output of any amplifier is determined by three things: (1) power supply voltage available to drive the output; (2) input signal amplitude; and (3) the gain of the amplifier. Divide into 10 V the minimum signal, in volts, that...
  14. hevans1944

    Strain gauge conditioner/load cell amplifier

    I agree. The Analog Devices AMP04 appears to be a better instrumentation amplifier than the venerable Texas Instruments (Burr-Brown) INA125 in many respects. I would try both of them and operate from ±15 VDC power rails. I haven't proposed any solutions yet, and probably won't, lest the state...
  15. hevans1944

    Strain gauge conditioner/load cell amplifier

    The "solutions" in the above two links neither use nor require an arduino or any other mcu. Both are analog circuits. To be clear, are you trying to reverse engineer the mantracourt product and build one for yourself with a 0 to 10 V DC output? Is the form factor (size) an important parameter...
  16. hevans1944

    Component getting too hot and I dont know why

    Don't think I have ever seen a comparison such as you describe. The heat transfer is from the flat case (tab) of the semiconductor device to a flat area on the heat sink. The bolt securing the two has very little influence on the heat path, ideally none in the case of plastic (Nylon) hardware...
  17. hevans1944

    Most inexpensive method for detecting if some current is flowing in 120VAC or 240VAC PCB Trace

    No, there are other options available to sense the AC current in a PCB trace. All that I am aware of create a small AC analog voltage that you must then amplify, condition, and use to set a threshold on/off current. The Allegra device integrates all that and provides galvanic isolation so its...
  18. hevans1944

    Component getting too hot and I dont know why

    Okay, just don't get carried away with the size. There are several varieties that are made for directly mounting on the tab. Your task is to calculate which one is best suited for your application. Assume 2 W dissipation, TJ = 125 C, TA = 25 C. A heat sink having a sink-to-ambient air heat...
  19. hevans1944

    Component getting too hot and I dont know why

    You are neglecting the thermal resistance between the 7505 tab and the ambient air. This is NOT zero or you would not be able to hold your finger on the tab and declare it "suuuuuper hot". From the TI datasheet: NOTE 1: Maximum power dissipation is a function of TJ(max), θJA, and TA. The...
  20. hevans1944

    Component getting too hot and I dont know why

    Heat sinks involve a huge amount of theory to "get it right" but often just "ballpark estimates" and experience will suffice. Look for some basic thermodynamics courses first to get a firm grasp on what heat is, how it is generated, and how it is conducted from one location to another. You need...
Top