Circuit Lighting :
Led Flasher LOW VOLT
Lighting Circuit page 01
Home
Power Supply Switching Regulator
Circuit Power Supply Regulator
Circuit Inverter and DC/DC Converter
Home
Circuit Project Electronic(blog)
Light Meter
Light Relay Switch
Light Switch
Lighting
lighting meter
lighting senser
Power Supply Circuit
Switching Power Supply
DC to DC Converter
Inverter circuit
Sitemap
www.circuitpowersupply.com
The following schematic is of the discrete component replacement for the LM3909.
The values of the components were chosen to match those in the integrated circuit however resistor R5 is a guesstimate fit as the Q2 portion of the circuit as Q2 in the integrated circuit is a "current mirror" which is a type of current regulator.
The Q2 portion of the circuit could not easily be duplicated using individual transistors but could be replaced with dedicated current mirror device.
Discrete Component LM3909 Circuit Notes
The values of the resistors in the discrete circuit can be adjusted to change various parameters of the circuit. (There is plenty of room to experiment with this circuit.)- The operation of the discrete circuit is exactly the same as the integrated version with the exception of transistor Q2. For more information please refer to the original device data sheet in the link above.
- The LED is the output device of the circuit and flashes at the rate determined by the oscillator.
- Capacitor C controls the basic flash rate of the circuit as it does in the integrated circuit. (The circuit above operated at a frequency of approximately one hertz with a capacitor value of 150 microfarads.)
- Resistor R1 - Higher resistance causes a longer but less intense flash.
- Resistor R2 - Controls the flash rate; The larger the resistance the slower flash rate.
- Resistor R3 and R4 - Can be increased causing the circuit to draw less current and slowing the flash rate slightly. These resistors should be equal in value. (The circuit showed no ill effects when R3 and R4 were increased to 820 ohms.)
- Resistor R5 - As mentioned earlier this resistor is a guess fit but seems to work fine at 1000 ohms. A lower value might increase the flash intensity.
- Pin #1 has been omitted from the discrete circuit as reducing the value of resistor R2 to 4,700 ohms would have the same effect as using this pin to increase the flash rate.
- The integrated circuit contains a Zener diode - D1. This diode has been omitted from the discrete version as it appears to serve no function when the circuit is operated from 1.5 or 3 volts.
This circuit has not been tested in any other mode other than that shown in the above schematic. There is no apparent reason that it shouldn't work in the other circuits shown on the LM3909 data sheet if the zener diode D1 is replaced.