| T O P I C R E V I E W |
| milk1995 |
Posted - Jul 08 2017 : 05:05:44 AM
Please look at the following circuit:
Download Attachment:  7.8.2.png
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This circuit is based on BC547 NPN#65288; http://www.kynix.com/uploadfiles/pdf8827/BC547A.pdf #65289;, I would like to ask that:
In the given circuit what will be the voltage and current the D1 led will revcive? I need to replace the led to get at least 5v 2A current at the place? What would be the changes in the circuit and how is it done? Can I get 2A directly out of a 555 ?
Please give me some help! Thanks.
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| 3 L A T E S T R E P L I E S (Newest First) |
| audioguru |
Posted - Jul 14 2017 : 1:57:44 PM
You will not get 2A from a little 9V battery that powers the circuit.
It is a horrible circuit:
1) I do not think the electret mic (it is not a condenser mic) will work when its voltage is clamped to only 0.6V by the base-emitter of the transistor.
2) The transistor will do almost nothing since it is turned on all the time. Then the 555 will not be triggered. |
| milk1995 |
Posted - Jul 09 2017 : 10:20:10 PM
Hi,Aaron
Thanks for you kind suggestions. I am beginning to research IRLU3410. |
| Aaron Cake |
Posted - Jul 08 2017 : 10:43:10 AM
According to the data sheet, a 555 timer can at most supply or sink 200mA at its output.
R=V/I so assuming a LED voltage of 1.5V then you are looking at about 7mA to drive that LED.
If you want to get more output from the 555 timer, you need to drive a MOSFET or transistor with the 555 to sink the current.
By far the dead easiest is to use a logic level MOSFET. No additional driver circuitry is required. My favourite is the IRLU3410. Output of 555 goes directly to gate. Also connect 1M resistor from gate to ground to bleed of internal capacitance. Source to ground, drain to cathode of LED while anode of LED connects to =V with appropriate resistor. |
