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  1. hevans1944

    gas detection system

    Maybe the one he has does do what he wants, but he also said this was a new project. The one he has is a little pricey at $6000 or so. So I think he is looking around for a less expensive alternative. JMO, but it would make sense to explore options. Youse guys would not believe how much I had to...
  2. hevans1944

    More efficient LDR "dark" switch?

    Colin's circuit should have worked with the BC547 transistors. See attached datasheet. The 2N2222 is a small-signal, higher-current transistor, whose gain increases significantly with increasing collector current, but you need gain at reduced collector current. See attached datasheet. If you...
  3. hevans1944

    gas detection system

    Which gasses do you want to detect? What is the minimal detectable concentration? What is the maximum detectable concentration? Do you need on-board data logging or just a visual display of the concentration? Do you need wireless (remote) data readout? How much are you prepared to spend? Is...
  4. hevans1944

    ATSC Over the Air decoder circuit for use with raspberry pi

    I would start my quest by reading what this liba52 open-source ATSC software project is all about. You will need an ATSC tuner to capture the HDMI video that you want to stream to your LAN through the Raspberry Pi. I have no idea whether or not the RPi is up for that or not.
  5. hevans1944

    How do I increase energy flowing into a Capacitor?

    I have been interested in, and sometimes professionally involved with, electromagnetic launchers since I was a teenager. A few years ago, one of the scientists that I had worked with bragged about a rail gun his team had built that he said was capable of launching "one pound to Jupiter!" At the...
  6. hevans1944

    How do I increase energy flowing into a Capacitor?

    Ah! Coil guns. Those are fun to play with, and relatively "safe" if proper precautions are made working around the electrical components. The problem is you can't really accelerate a projectile to "interesting" velocities like, say, hypersonic with just one coil. Discharging a capacitor into a...
  7. hevans1944

    12vdc Pulse Timer

    @Kiwi So how do you determine the headlights are on? Are the cornering lamps powered from the same circuit that provides power to the headlights? Why is this supposedly a difficult problem? I will admit I know virtually nothing about modern automobile wiring. The last thing I actually worked on...
  8. hevans1944

    How to control 80 relays using ardrino

    Yeah, me too. I might reply again when there is some sense to be found here... maybe after I see a system block diagram complete with component specifications. Until then, I'll go spin my wheels somewhere else.
  9. hevans1944

    12vdc Pulse Timer

    Either way, a diode on each indicator lamp to detect and steer the turn signal to added circuitry for the timing delay and to activate the cornering lamps should work. Do both cornering lamps come on at the same time, or just the one in the direction being turned into?
  10. hevans1944

    How to control 80 relays using ardrino

    Transformers are pretty efficient, perhaps 98% unloaded dropping to maybe 80% to 90% fully loaded. It depends on the resistive losses in the windings and core losses (from magnetic hysteresis, mainly). Your best bet would be to temporarily load up the secondary to get 50 A at 30 V using a...
  11. hevans1944

    How to control 80 relays using ardrino

    @Farukh Khan Thank you for your detailed and intelligent reply to my questions. I feel somewhat reassured that you won't burn down your concrete abode. The biggest problem I see you having is: How do you do the actual wiring between the relay contacts and the appliance circuits those contacts...
  12. hevans1944

    Homemade Capacitor

    @Lavaguava Hydrogen fuel cells have been used for years by NASA to power outer space Earth orbit and Moon excursions. They have the advantage of producing only water (which can be re-cycled for human consumption) when the hydrogen fuel is "burned" (oxidized) in the fuel cell. They will probably...
  13. hevans1944

    Looking for receptacle lube

    I hate when that happens! That's what switches and contactor relays are for.
  14. hevans1944

    Thyristors and AC DC Diode Converter help

    You are going to have to do some real troubleshooting to replace this. First, no matter if NO13RH06 is an obsolete or factory part number, it may mean the stud is Reverse connected to the cathode instead of the anode because of the R in the part number. Some power supplies did this so the heat...
  15. hevans1944

    Conditioning Electronics

    No excuses needed here, Adam. We all make mistakes. Like me forgetting (or ignoring) for at least a month that the PIC10F206 uses pins for multiple purposes, and then not programming accordingly. Once I spent an entire day (with pay!) "troubleshooting" a complex op-amp circuit, wondering why...
  16. hevans1944

    How to control 80 relays using ardrino

    This sounds like an accident waiting to happen after everything is built and the power is applied. Please answer these questions: 1. Are your "equipments" household appliances powered from wall sockets? 2. If you are powering your "equipments" not from a wall socket but instead from a power...
  17. hevans1944

    Homemade Capacitor

    The requirement was self-imposed. @Lavaguava is doing this (or at least trying to do this) as part of an entry to the 2015 Google Science Fair, which entries closed early in May of this year for the 2015 world-wide competition. Regional winners will be announced in July. Well, if @Lavaguava and...
  18. hevans1944

    Inject sound to a phone landline

    I agree with @AnalogKid with regard to placing any kind of transformer across the telephone line, thereby completing an "off hook" DC circuit that the TELCO will probably recognize, even if it doesn't provide enough current to trigger a dial tone. The TELCO automagically and periodically tests...
  19. hevans1944

    Homemade Capacitor

    One farad is an enormous amount of capacitance. Charge is what you put on it, electrically, and can be any value up to where the capacitor fails by arcing through the dielectric. Q (charge) equals C (capacitance) multiplied by V (voltage across the capacitor): Q = CV. That's good advice on how...
  20. hevans1944

    Capacitor question

    Not really. These things were routinely replaced, bad or not, along with the points and the distributor rotor because (1) it is easy to do so and (2) if it is bad it would save time not having to remove the distributor cap again. Those particular capacitors are damned reliable because they have...
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