Posts

Showing posts with the label diodes

Para saki the QRP Transceiver fact Diodes Circuit Diagram

Image
This circuit is a dream of 40 years was conducted, a transceiver QRP (low power) done without transistors, IC or valves, its creator just used diodes. The receiver has little gain, but works well for strong signals via the audio amplifier which is very effective.I believe this transceiver is at least very curious, though precarious it sure works and shows that the electron has no limits. Para-saki the QRP Transceiver fact Diodes Circuit Diagram Parasaki the QRP Transceiver fact Diodes Circuit Diagram

Diodes

Image
Function Diodes allow electricity to flow in only one direction. The arrow of the circuit symbol shows the direction in which the current can flow. Diodes are the electrical version of a valve and early diodes were actually called valves. Forward Voltage Drop Electricity uses up a little energy pushing its way through the diode, rather like a person pushing through a door with a spring. This means that there is a small voltage across a conducting diode, it is called the   forward voltage drop   and is about 0.7V for all normal diodes which are made from silicon. The forward voltage drop of a diode is almost constant whatever the current passing through the diode so they have a very steep characteristic (current-voltage graph). Reverse Voltage When a reverse voltage is applied a perfect diode does not conduct, but all real diodes leak a very tiny current of a few µA or less. This can be ignored in most circuits because it will be very much smaller than the current flowing in th...

c Use of diodes

Image
Use of diodes as surge suppressors Contactors are generally designed in such a way that a slight contact welding during closing is forced open again by the back pressure springs of the contacts during de-energization. Diodes can reduce the drop-out speed of a magnet system to such an extend, that the abovementioned slight contact welding cannot not be opened anymore In the extreme case the low drop-out speed caused by the diode can lead to a so-called two-step drop-out. This means that following the first contact opening, another short, weak closing of the main contacts may happen during the breaking process. This second closing (during the arcing time) can lead to welded contacts. Since two-step drop-out cannot happen with size S00 3RT1 contactors, diodes as surge suppressors are offered for this size only. From size S0 upwards diode assemblies (series connection of diode and zener diode), RC-elements or varistor have to be used as surge suppressors. Some companies on the market o...

Temperature Sensing Diodes Selector Circuit Diagram

Image
Low-cost semiconductor diodes such as 1N914, 1N4148 and 1N400X can be used as temperature sensors in applications where high accuracy is not required. They can be mounted on transistors, power diodes, transformers, heat sinks, rechargeable batteries, crystals, PCB, etc to monitor their temperature. It is highly desirable to use temperature sensors with linear temperature characteristics and the mentioned diodes are best suited for that. To use them as temperature sensors, these diodes first need to be sorted according to their temperature coefficient. (Please refer ‘Signal Diode-Based Fire Alarm’ circuit idea published in February 2013 issue to understand how these diodes can be used as temperature sensors.) This circuit can help quickly sort different diodes based on their temperature coefficient. Circuit and working The circuit diagram of the device for selection of temperature-sensing diodes is shown in Fig. 1. The circuit is built around step-down transformer X1, voltage regulator ...