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Handy Time Delay With Relay Output

This circuit is designed to provide delayed relay switching action at power on. The delay is a function of the time constant produced by the combination of R1 and C1. At power on, C1 charges slowly via R1 and the coil of the relay. When the voltage across C1 exceeds both the base-emitter voltage of Q1 and the gate trigger voltage of the SCR, gate current flows. This fires the SCR and switches on the relay. At power off, diode D1 rapidly discharges C1 through the 100O resistor, so ensuring that every time the circuit is restarted, as in a temporary outage, the delay time is maintained.

Just about any NPN transistor can be used for Q1, since after SCR1 fires, it is effectively out of the circuit. In fact, the only part that’s still active after SCR1 turns on is the relay. You can’t get much simpler than that! This circuit can be used to delay speaker turn-on, so avoiding the “thump” that occurs in some stereo systems at power on. A 5-second delay is enough for this application, requiring approximately 560kO for R1 and 10µF for C1. Another application might be as a motor protector in a short power outage.
Author: R. Besana – Copyright: Silicon Chip Electronics

link : http://www.extremecircuits.net/2010/06/handy-time-delay-with-relay-output_17.html

Be the first to comment - What do you think? Posted by admin - January 4, 2011 at 1:42 am

Categories: Electronic Control, Timer Tags: basic timer, Time Delay, timer relay

Simple scheduling tool

IC 555 to IC Timer (scheduling IC) or IC timer.Which may be can be considered quite unique features.To use the time to bring the device resistance.
For the period that desire.
This circuit 555 to the IC number on the circuit Mono Stable. Multi Vibrator. or Delay circuit with operating environment that provides a second output level be The voltage is low (logic “0″) and high-level voltage (logic “1″). When you click the switch S1 pin 2 of the IC will be shot down ground. The motive for the IC1 with low voltage (logic “0″). Resulting in the output pin 3 of IC voltage levels at higher or equivalent supply. it making light LED1. Experience in the scheduling itself. And in setting up or slow down time depends on the R2, C1.And VR1 to adjust the scheduling easier.

Be the first to comment - What do you think? Posted by admin - September 7, 2010 at 12:47 am

Categories: Timer Tags: Astable Timer, basic timer, timer alarm

Timer set for 30 minutes by transistor

This circuit is based on learning of the discharge and charge of the C, which can be used as a timer circuit and can be applied in the off electrical appliances. The application has also put relay instead of LED can be enabled.
When you click the switch S1 will cause LED1 light told state ready to run S2 is a timer switch. On press switch S2 current will flow to the C1 charge fully. Then to discharge out through R2 to limit current flow to the bias for transistor Q1. Q1 and Q2, which work together to Darlington Compound. To have growth rates high to drive the LED2 light over time as C1 discharge all Q1 and Q2 stops LED2 is off if you want the timer circuit is longer. Then add the C1 and if you want a little time. to reduce it to C1.