Tuesday, February 22, 2011

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LED Pulser Circuit Using Op-Amp LM358

This circuit operates a LED in pulsing mode, LED goes from off state, lights up gradually, then dims gradually. This operation mode is obtained by a triangular wave generator formed by two op-amps contained in a very cheap 8 pin DIL case IC. Transistor Q1 ensures current buffering, in order to obtain a better load drive. R4 & C1 are the timing components: using the values shown in the parts list, the total period is about 4 seconds.
LED  Pulser  Circuit Using Op-Amp LM358
  • The most satisfying results are obtained adopting for R4 a value ranging from 220K to 4M7. Adopting for R4 a value below 220K, the pulsing effect will be indistinguishable from a normal blinking effect.
  • Voltage supply range can be 4 to 6V: 4.5V is the best compromise.

List Component of LED  pulser  circuit
R1,R2  : 4K7
R3     : 22K  
R4     : 2M2 1/4W (See Notes)
R5     : 10K 
R6     : 47R 
C1     : 1µF Polyester Capacitor
D1     : 5mm. Red LED 
IC1    : LM358 Dual Op-amp
Q1     : BC337 

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