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  1. darrins

    drag race christmas tree

    The 555 timer should be wired for astable mode for your application. I believe that there should be two timing resistors for astable mode and that pin 7 is wired at the junction of these two resistors. Here's a good website for a tutorial on 555 timers...
  2. darrins

    temp sensor cooling system

    I just remembered that these temperature IC's have an upper range of about 300 deg Fahrenheit (about 150 deg C). This is probably good enough for your project, but just another thing to keep in mind. I think a typical automobile will overheat at about 240 deg F, but that's a water cooled...
  3. darrins

    temp sensor cooling system

    Have you considered using the LM34? It's already calibrated in degrees Fahrenheit. I'm from the states, so I prefer the English units. ;) It seems you could just use a simple comparator circuit. The following document has a lot of specs and some good application examples. See their...
  4. darrins

    HELP! 555 timer to control pump

    I'm not sure exactly what you mean by "protective ground". When I built my other power supply, I used and old 3-pronged power cable from one of my old computers. It is my understanding that the middle prong is earth grounded when plugged into an electrical outlet. I wired this middle prong to...
  5. darrins

    HELP! 555 timer to control pump

    I didn't notice any improvement with 47 uF. I tried a couple of large caps (1000 and 2200 uF) with varying results. Is the decoupling capacitor suppose to handle the sudden voltage requirement of the pump at startup? If so, shouldn't this capacitor be close to the supply leads of the pump...
  6. darrins

    HELP! 555 timer to control pump

    "Try an electrolytic capacitor say 2200
  7. darrins

    HELP! 555 timer to control pump

    Thanks for the advice. I'll try it. The "dip" in voltage seems to be only a transient that lasts while the pump is starting up until it gets to its steady state running condition. I'm not sure what value of capacitor I should use. I suppose I'll just experiment until I get it working...
  8. darrins

    HELP! 555 timer to control pump

    I am new to electronics, so I apologize for my ignorance. I working on a project that involves emptying a small tank of water using a solenoid valve. The valve is opened for a certain amount of time by using a 555 timer and a reed relay. When this timer goes low, the valve is closed, and...
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