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  1. darrins

    Mini golf cart from UPS batteries

    Ante, The batteries are connected in series. The voltage across both batteries measured about 9V. The "bubbly" one measured 7V and the other one measured 2V. Something's definitely wrong there. I would expect them to be more balanced. I'll hook everything back up and see if one of them...
  2. darrins

    Mini golf cart from UPS batteries

    At work the other day, we smelled something burning in our server room. The culprit -- an old uninterruptible power supply (UPS). It's more cost effective for us to just throw these things away and buy new ones than try to repair the faulty unit. One man's trash is another man's treasure, so...
  3. darrins

    On/Off heater controller using triac

    I don't mean to beat this into the ground, but I'm very curious. What would happen if the pulses were sent to the triac driver such that they never crossed the zero intercept of the AC signal? In other words, what would be the output of the driver if the pulses were entirely contained within...
  4. darrins

    Dual Lab Power Supply

    audioguru, Do you have a schematic for your LM317 regulated battery charger? I built my variable power supply using a LM317 (1.5 to 30V). Very similar in design to this one: http://electronickits.com/kit/complete/powe/ck402.pdf Perhaps my design could be modified to accomodate the battery...
  5. darrins

    Dual Lab Power Supply

    A few questions about this supply. It has 2 primaries and 6 secondaries. Where do you find transformers like this? And why the need for all the secondaries? A theoretical question: If you have a single set of AC leads split between two transformers, T1 and T2, will a load attached to T1...
  6. darrins

    On/Off heater controller using triac

    I think I may have found my "poor man's" solution. I'll just use my temperature sensor and comparator circuit to control ON/OFF of the dimmer switch and adjust the pot on the dimmer until I'm happy with the response characteristics. I may try my hand at controlling it with PWM to the...
  7. darrins

    On/Off heater controller using triac

    I guess what I'm really building is a solid state relay for my heater, like this one from Tony van Roon's tutorial on relays: From: http://www.uoguelph.ca/~antoon/gadgets/relays/relays.html In my application, the heating element would be the load, instead of the light bulb. Correct me if...
  8. darrins

    On/Off heater controller using triac

    Ok. I'm starting to feel really stupid. I just want to use the triac so I can limit the power to my heater (via phase control). In other words, I probably won't be varying the phase angle while my heater is ON. I'm building a VERY crude bang-bang controller. When my voltage from my...
  9. darrins

    On/Off heater controller using triac

    Oops. That last post didn't enter the entire url correctly. Here's the image.
  10. darrins

    On/Off heater controller using triac

    I'm can't post an image of my circuit (I don't have a website), but I can post a web page of something very similar. Instead of using a thermisor to measure temperature, I'm using an IC (LM34), which outputs 10 mV/deg F and is much more linear than the thermistor. I don't know how this type...
  11. darrins

    Electronic weighing system

    I considered using a timer. This is definitely a more economical and simpler approach. My appliance will dispense different kinds of powders with different characteristics, e.g. density, so I'll have to experiment with this to see if it is accurate enough. I appreciate the feedback. Darrin
  12. darrins

    On/Off heater controller using triac

    Thanks Ante. I ordered a couple of free sample MOC3041's from Fairchild. I found a schematic in the data sheet that has me a little confused. On page 5 of http://www.fairchildsemi.com/ds/MO/MOC3041-M.pdf, there is a circuit that shows 115V AC connected to the MOC3041. At pin 2, there is a...
  13. darrins

    On/Off heater controller using triac

    Just from experimenting with the heating element with 110V AC, my water tank gets too hot, too rapidly. The resistance of this heating element is VERY low, about 20 Ohm. From Ohm's law, this would be around 600 W (if my math is correct). So, I need even less power than 600W. I only got the...
  14. darrins

    On/Off heater controller using triac

    In a previous post, I asked about designing a controller to regulate the temperature of a small tank of water. Ante suggested using a triac to control power sent to the heating element. After some reading, I also agree that this is a good technique; however, I haven't been able to find any...
  15. darrins

    Electronic weighing system

    I'm working on an appliance that dispenses a powder from a hopper using a feed screw. I want to control the dispensed quantity by measuring the weight loss of the hopper. This change in weight will be on the order of 7 grams to 40 grams. I figure that this could be done by either: a) using a...
  16. darrins

    source for strain gauges

    Anyone know where I can buy cheap metal foil strain gauges? I'm trying to make a "poor man's" load cell. Thanks. Darrin
  17. darrins

    idea of infinite energy

    I agree with audioguru. If you apply apply a huge force to a stationary object for a nanosecond, you probably won't move the object. To move a large object (do some work), you have to apply a considerable impulse. This is the area under the force vs time curve. Even though you have a large...
  18. darrins

    Voltage req to heat small amt of water

    Any water heating experts here? I have a flexible heating element that is wrapped around an aluminum cylinder that contains water. It contains about 12 oz of water at room temperature. I want to heat the water to around 100 degrees Fahrenheit from an initial temperature of about 74 degrees...
  19. darrins

    Mains current detection

    I like the Moderator's idea, but would this device accidentally get triggered by other noisy power tools? (obviosly the power to YOUR device would have to be ON). Just something to keep in mind. Here's a poor man's solution: Do you have to pull a trigger to operate the saw? If so, can you...
  20. darrins

    drag race christmas tree

    Here's a cool website that shows an animation of a 555 timer in astable mode. http://www.williamson-labs.com/480_555.htm To stop the timer, you can ground pin 4 (reset). Cheers. Darrin
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