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- Low Voltage Latching Relay Driver
Using some small super capacitors, this circuit can latch and unlatch a mechanical relay with 10 amp contacts, from a small 3 volt power source. By using a latching relay, power can be
controlled to a load with a tiny battery. (added 7/06)
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- N-CH AND P-CH TRANSISTORS FORM PUSH-PULL DRIVER
This circuit can produce high speed output signals with fast rise and full times. The unique change pump action allows the voltage of the upper P-ch device to range from millivolts to
hundreds of volts. The output current is only limited by the rating of the transistors. I have used this circuit beyond 2MHz.
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Ramping LED Driver
The circuit below was designed to drive a LED with an intensity
ramping mode. Two 555 timers generate two different triangle waveforms.
The upper device generates a 10KHz signal while the lower unit produces a
1Hz signal. The two signals are fed to a voltage comparator. The result
is a pulse width modulation (PWM) signal, which with the aid of the FET,
drives the LED in such a way that its average light output slowly ramps
from about zero light to maximum and then slowly dims back down. The
circuit should operate over a supply voltage ranging from 3v to 12v. You
can easily vary the ramping time by changing the value of the 1M
resistor. For an interesting effect, you can place a 1N4148 diode in
parallel with the 1M resistor, with the cathode (banded end) side
connected to pin 3.
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Reduced Power Relay Driver
Aug 3, 2008
Relays can handle a lot of power. However, for certain power sensitive
designs you would like to reduce the power needed to hold a relay closed.
The circuit below performs such a task. It uses a single CD4093 quad NAND
gate. When the on logic input signal is detected, the relay is first
pulsed on for about 500ms. This is sufficient time to insure the relay is
fully closed. After that initial pulse the relay is then driven with a
square wave signal, whose duty cycle can be adjusted. The signal duty cycle
can be adjusted from about 10% to 90%. In most cases a 50% duty cycle will
hold the relay closed. This reduces the average DC current required by the
same factor, which means a 4:1 reduction in power. The circuit can operate
over a wide 3v to 15v range.
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- SQUARE WAVE DRIVER HAS FLEXIBLE OUTPUTS
This circuit can produce an output signal ranging from DC to 100KHz. It can source a voltage ranging from 1v to 30v. It can sink a voltage ranging from zero volts to 30v. It can drive up to
200ma of current and can even be switched to a floating tristate output.
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