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  • Simple Power LED Linear Current Regulator, Revised & Clarified

    Have now replaced this with a correctly marked image. Thanks for pointing it out to me.

    You are correct— I did not invert my results (1/1 ohm + ½ ohms=1/1.5=0.666 ohms of resistance)

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  • Charge Your Car Battery With Laptop Charger!

    I understand that the multimeter here is measuring the current flowing into the car battery, but can you explain what purpose this information serves? Simply knowing what the current is may not by itself have any bearing... Unless it does somehow. And if so, can you explain it? In other words, if I do NOT use a multimeter to measure the current btw the laptop adapter and the car battery, what will I be missing? (esp. given that I know the adapter can't put out more current than the battery can hold, just more voltage, which I am already measuring through the volt meter attached to the car battery in your design). Thanks!

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  • KDS4444 commented on Grathio's instructable Choosing The Resistor To Use With LEDs9 months ago
    Choosing The Resistor To Use With LEDs

    ...and hook them up in parallel, not in series...

    Also consider this: the little bouncer may actually get run over if the current is too fast-- i.e., you may destroy your resistor if it either isn't rated to withstand that kind of fast current OR if it doesn't provide enough outright resistance to the flow of the current. A resistor of 100,000 ohms rated for a certain wattage will be okay in a place where a resistor with the same wattage rating but only 5 ohms of resistance will get burned up by the same amount of current. A small bouncer who is able to say "no" to most everyone will be able to handle the situation without burning up, as will a "big" bouncer who says "yes" to lots of people. A fast current through a small (low wattage) resistor with a low level of resistance is what makes the resistor g...see more »Also consider this: the little bouncer may actually get run over if the current is too fast-- i.e., you may destroy your resistor if it either isn't rated to withstand that kind of fast current OR if it doesn't provide enough outright resistance to the flow of the current. A resistor of 100,000 ohms rated for a certain wattage will be okay in a place where a resistor with the same wattage rating but only 5 ohms of resistance will get burned up by the same amount of current. A small bouncer who is able to say "no" to most everyone will be able to handle the situation without burning up, as will a "big" bouncer who says "yes" to lots of people. A fast current through a small (low wattage) resistor with a low level of resistance is what makes the resistor get hot/ incinerate!

    I am sorry I didn't notice this reply two years ago. Let me see if I can get this right: what happens when you attach such LEDs to a 5V 700mAh power supply is that the LEDs will attempt to draw all the power they can from the power supply-- that supply is only RATED at 700 mAh, and so the POWER SUPPLY will start to overheat! (to say nothing of the LEDs, which will also likely go kaput). The mAh rating of any power supply is the amount of power (current) that it can safely PROVIDE without damaging ITSELF, it is NOT a measure of how much "power" or "current" it "provides" (per se). If your circuit only draws 20mAh from a 700mAh power supply, that's great! If your circuit tries to draw 1000mAh from the same power supply, the supply will be damaged, not the...see more »I am sorry I didn't notice this reply two years ago. Let me see if I can get this right: what happens when you attach such LEDs to a 5V 700mAh power supply is that the LEDs will attempt to draw all the power they can from the power supply-- that supply is only RATED at 700 mAh, and so the POWER SUPPLY will start to overheat! (to say nothing of the LEDs, which will also likely go kaput). The mAh rating of any power supply is the amount of power (current) that it can safely PROVIDE without damaging ITSELF, it is NOT a measure of how much "power" or "current" it "provides" (per se). If your circuit only draws 20mAh from a 700mAh power supply, that's great! If your circuit tries to draw 1000mAh from the same power supply, the supply will be damaged, not the circuit. Power LEDs don't limit their own current draw-- this must be managed by some kind of external circuit. Obviously, hooking a power LED up to a power supply that has a very high mAh rating will quickly destroy the LED, even if the voltage provided by that supply is within specs (unlike a regular LED, which will be fine no matter what the current supplied is-- so long as that current draw is lower than the rating of the power supply, the power supply will not be damaged either).

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  • KDS4444 commented on Dustint66's instructable Black and white headshots made simple9 months ago
    Black and white headshots made simple

    What would be great is if you could post an overhead diagram showing where your lights, camera, and stool are placed for each of these shots. It would also be handy if you described exactly what a "soft box" is for those who see your video and are not professional photographers. Thanks! I intend to use what I've learned in this video to take some headshots today.

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