Showing posts with label LED. Show all posts
Showing posts with label LED. Show all posts
Sunday, May 5, 2013
Three Flashing LED Doorbells For The Hearing Impaired
When
the push switch is operated - the buzzer will sound and the LEDs will
begin to flash. For the hearing members of the household - the buzzer
acts as a regular doorbell. It also re-assures the visitor that the
doorbell is working.
When the push switch is released the buzzer will stop - but the LEDs will continue to flash. The length of time they will go on flashing is set by the values of R2 & C1. With the values shown in the diagram - the LEDs will flash for a further 30 seconds or so. If you make R2 a variable resistor, you can adjust the time period. If you want longer than 30 seconds - increase the value of C1 or R2.
When the push switch is released the buzzer will stop - but the LEDs will continue to flash. The length of time they will go on flashing is set by the values of R2 & C1. With the values shown in the diagram - the LEDs will flash for a further 30 seconds or so. If you make R2 a variable resistor, you can adjust the time period. If you want longer than 30 seconds - increase the value of C1 or R2.
The
main difference between this circuit and the last one - is the
addition of the two transistor switches. The switches will each flash up
to 15 groups of 3 LEDs. And - because they are getting power directly
from the battery - the LEDs will glow at their full brilliance.
Sunday, September 2, 2012
40 Segment LED S-Meter
40 Segment LED S-Meter Circuit
Provide your radio with a actual cord signal, again acclimatize the HIGH LEVEL pot to the beginning of anecdotic the aftermost LED (all LEDs on). Remove the arresting completely, again acclimatize the LOW LEVEL pot to the beginning of no LEDs illuminated.
If your radio's S-meter achievement is greater than 5 volts, you mau ambition to alter the HIGH LEVEL pot with a 10K resistor, and accommodate pin 6 of the right-most 3914 with the cathode of a 6.1 volt zener diode, pulled up to 13 volts with a 1K resistor. The anode should be affiliated to ground. You may use a college voltage zener if necessary.
This agreement provides 10ma per LED segment. Change the ethics to the resistors and pots to change the drive accepted to the LEDs. R1=12.5/I R2=25/I R3=37.5/I R4=50/I area I = the adapted LED current
Monday, May 31, 2010
20 LED AUDIO VU METER
This circuit has 3 main sections, an inverting op-amp amplifier, a rectifier and LED display. The input can be from almost any low level source, but if not using an electret microphone, then omit R1 as it's not necessary. The gain of the amplifier based around IC1 is controlled by VR1. The output is rectified by D1,2 and filtered using C4,R6.The final stage is a standard design for the LM3914. Alter R8 to control LED brightness but be careful not to over-drive the IC's. It's recommended that you don't
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