The Q-Switch driver for an old Yag laser died. A replacement was >$1000 so we built our own for <$300 (picture and schematic below). The specs were >= 20W into a 50 ohm load at 68MHz. The rep rate had to be adjustable between 100Hz and 100KHz and have a TTL output to synchronize the output with other equipment. I had never made a RF amplifier befo
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re so for me that would be the tricky part. I started by ordering a 3. 3V CMOS oscillator, CPPC4-LT5RP ($8. 14), from and having them program it for 68. 000MHz. The square wave oscillator worked well but couldn`t drive a 50 ohm load. I AC coupled the oscillator to a MAX4258 video driver/multiplexer. The AC coupling centered the oscillator at GND and the driver can drive a 50 ohm load. The multiplexer will later be used to quickly turn off the oscillator for about 6us (to q-switch the laser). If I block all frequencies above the fundamental I can turn a square wave into a sine wave. An article on DDS IC`s in Circuit Cellar pointed me to The filter software was easy to use and free. I was able to make a 5th order low-pass to block everything above 72Mhz. The 68MHz fundamental will pass but all the harmonics will be attenuated (Ex: The third harmonic, 204MHz, is attenuated by 50db). Now I have a 68MHz sine wave that`s about 3Vpp (13dbm). Note: I need 20W (43dbm). We searched around and found the RA30H0608 from ($73). Its specs are 68-88MHz, 30W output, 12V power supply, and it has a gate pin to modulate the output (i. e. control the gain). I used a trim pot to set a DC voltage, buffered it with an op-amp configured as a voltage follower, and sent it to the gate pin on the amplifier to control the gain. Note: Turning the RF off via the gate pin was slow (about 10us) so I used the mux on the video driver IC to turn the RF on and...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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