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Post by hellomoo on Dec 25, 2008 22:35:18 GMT -8
Your circuit works very well. But IC555 is quite warm and 150 ohm is too hot. How can I fix this problem?
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Post by Gary Lecomte on Dec 26, 2008 6:35:14 GMT -8
Your circuit works very well. But IC555 is quite warm and 150 ohm is too hot. How can I fix this problem? You Must have done Something Wrong. It should Not get hot. Gary |
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Post by hock on Jan 21, 2009 10:37:29 GMT -8
Hi there..
About the Heating post. i have build the same unit, etched a board put it together,the schematic says lm555 i checked a dataspec and the NE555 is the same ic. I made about 3 coils one from 16 gauge about 10 loops diameter is about 20 cm did change the cap to 100k still the same problem.tried 15 loops same diameter with coms cable ( piece of cat 5 ) and ;( ...150 ohms getting hot and LED not turning off.. Any ideas ?
Thanks Jared
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Post by Gary Lecomte on Jan 23, 2009 6:57:35 GMT -8
Hi there.. About the Heating post. i have build the same unit, etched a board put it together,the schematic says lm555 i checked a dataspec and the NE555 is the same ic. I made about 3 coils one from 16 gauge about 10 loops diameter is about 20 cm did change the cap to 100k still the same problem.tried 15 loops same diameter with coms cable ( piece of cat 5 ) and ;( ...150 ohms getting hot and LED not turning off.. Any ideas ? Thanks Jared Any 555 is OK. The "LM" is made by National Semi, the "NE" is made by Signetics. If the LED is Not Turning OFF, You do Not have it set correctly to achive a Resonance and in that case, the resistor may get hot. In My Write-up, It says a 3 to 6 Turn Coil, 4 to 6 FEET Diameter or Square. 1) 16 AWG wire is a Bit Big. I would suggest a 20 to 22 AWG. 2) Your 20 Cm is TOO SMALL of a Diameter, But May work with around 12 Turns. 3) The 150 Ohm Resistor Could be increased to a 220 or 330 Ohm to reduce current flow, IF Required. *** I'll Try a Prototype Later Today and Post My Results using an 8 Inch (20Cm Coil.). UPDATE:Winding an 8 inch (20cm) Coil with 12 Turns of 22 AWG Enamel MAGNET wire, (Scramble wound and Taped to make a Rigid Coil) and using a .22uF cap Works Fine. With the 150 Ohm Resistor, Total Circuit Current draw is 90 mA. NOTE, I have No Resistor Heating Problem. (However, My 150 Ohm resistor is a 1/2 watt resistor in a 1/4 Watt Package.) ALSO, Recently I bought some 2 watt resistors, manufactured by "BC COMPONENT". The Operating Temperature of these resistors at 2 watts is OVER 300 Degrees. WHAT CRAP is that! DO NOT BUY ANY "BC COMPONENT" RESISTORS, If you can Avoid them. Changing the 150 Ohm Resistor to a 330 Ohm Resistor, Total Circuit Current Draw is 60 mA. But I find a slight Reduction in Sensitivity. ** IF you Use wire with a Vinal Insulation, it will have a LOWER Inductance, for the Same number of turns. *** I ONLY Recommend Enamel Wire. (The type used in winding Transformers.) |
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