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Flash Lights with HT2014L

This scheme is almost the same with a flash light with LM3909. In this scheme only requires IC HT2014L as a leader, and a resistor and LED. For voltage here need ration power around 4.5 V. You can apply this series to a wider scale in comparing the use IC LM3909. For the scheme are below:

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Simple Flash Lights with LM3909

This scheme in a simple flash light with LM3909, LM3909 IC where this as a central leader. This series is a need IC, a capacitor and LED as a light. You can apply this series as a garnish on the vehicle or as a toy. For the LED light you can use the appropriate color LED that you taste. Would better if you use two colors. Tension in this series is only using 1.5 V is a saver, you can use the battery as a source of tension. For the scheme are below:

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Single Supply Zero Crossing Detector With LM339

This scheme is called Zero-crossing detector using LM339, in principle, be used to convert without waves or other signals into square-wave, the output should be low if the input is negative, and if high if the positive feedback. Many zero-crossing detector using split supply (supply symmetrical), but this zero-crossing detector circuit requires only one supply, so suitable for battery-operated circuits.

schematic diagram source: Motorola Application Notes

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Audio Frequency Meter

A scheme in the audio frequency of 555 meters with a monostable multivibrator (one-gun trigger). A monostable multivibrator can act as frequency-to-voltage converter because it produces a fixed pulse width, with the level of repetition / density is proportional to the trigger input frequency.

Resistor R3, set the scope of work measurement, better use Rotary switch to select different values for different ranges. If the obstacles R1 set 1M generate 50Hz, 500Hz generate 100K, 10K produce 5000Hz. For ampere meter, you can use both analog or digital ampere meters. A cheap dual-slope ADC digital meters.

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Simple Switching Circuit with 555 for Negative Supply

This shematic is called Simple Switching Circuit with 555 for Negative Supply. In principle, the core of this series are located in the IC 555. If you need a negative for the op-amp or just need a negative bias voltage while operating from a single supply voltage (battery operation for example), this circuit helps provide a negative supply for you. Circuit that is based on the cost of 555 pump driven by the circuit switching. Here is a schematic diagram.

If you use 9V positive supply then the negative output will be around 8 volt, or if you use 12 volt positive supply the you’ll get around 11Volt negative supply. 100mA current could be drawn safely from the negative voltage output. This is enough for most op-amp or other small signal application. PCB to the scheme below.

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