Mutchus

One tool that I’ve been missing at my lab at home is function generator. They tend to be a bit expensive, so I haven’t bought one. I thought this might be a good opportunity to try and make one myself. I found a pretty common DDS (direct digital synthesis) chip, called AD9833. Then just strap a USB-enabled AVR micro there and maybe some analog electronics.   This board doesn’t do any of the special analog magic to allow for variable amplitude or offset for the signal. The output is fixed to 0-4v. I’m planning to make another completely analog board for adjusting amplitude and offset. [ ]

Use this circuit instead of a standard on-off switch. Switching is very gentle. Connect unused input pins to an appropriate logic level. Unused output pins *MUST* be left open!. First 'push' switches ON, another 'push' switches OFF. You can use 1/4 watt resistors if they are metal-film type. Any proper substitute will work for Q1, including the european TUN's. For C2, if you find the relay acts not fast enough, leave it out or change to a ceramic cap between 10 and 100nF. Parts List All resistors are 1/2 Watt and 5% tolerance. R1 = 10K R2 = 100K R3 = 10K C1 = 0.1µF, Ceramic C2 = 1µF/16V, Electrolytic D1= 1N4001 Q1 = 2N4401 (ECG123AP, NTE123AP, etc.) IC1 = 4069, CMOS, Hex Inverter (14069), or equivalent S1 = Momentary on-switch Copyright © Tony van Roon

About a year ago I came across an interesting article in Make Magazine about a guy who took his Fossil Wrist PDA and installed an Apple II emulator on it.   He was able to load many of the Apple II software titles and run them at regular speed.   The thought of having a fully functioning Apple computer on my wrist excited me enough to give it a try.      People that are attempting to do this should be familiar with the Palm OS as well as using jot or Graffiti 2 as an input method.   The Fossil Wrist PDA (now discontinued) features a tiny gray 160×160 pixel screen, the same number of pixels as most palm devices up to Palm III, with 16 shades of gray. The watch runs Palm OS 4.1 with its 66MHz processor and has a tiny stylus hidden in the watch clasp. It is able to carry out most PDA functions, and run any normal Palm OS-compatible application (up to 4.1). It features 8 Mb of RAM (about 7.7 Mb available to user) and 4 Mb of flash memory. Like other Palm OS de...

This adapter circuit can deliver up to 3A output voltage of 12V. The circuit can be used in cases when a current of more than 3A is required for the controller. IC regulators such high current rating are quite hard to find. The T1 transformer steps down the voltage of the rectifier bridge 12rms and D1 to produce a rectified voltage. The C1 filters the output of the rectifier produces a DC level. The passage of the series transistor Q1 (2N 3055) is biased by resistor R1 (680Ω). Since D1 is Zener breakdown region of the voltage across it is 12V. So the total output voltage of 12.7 V is constant (in theory). Zener voltage which is the most base emitter voltage of transistor Q1 Q1.Here take out the excess power needed. Notes . If 12V zener is not available ,use the nearest value. The transformer T1 can be as 23oV primary;15V/5A secondary step down transformer. The capacitors must be rated at least 25V. By changing the value of the Zener diode, different output voltages can be obtained f...

The LM3914 is a truly versatile component. Besides LEDs, only a few other components are needed to make the ‘bidirectional’ bargraph voltmeter shown here. The circuit is similar to a conventional bar display, but it offers a possibility to change the direction in which the LEDs are switched on. This may be useful, for example, when positive and negative voltages are measured. For a positive input voltage, the LEDs are switched on in the usual manner, that is, from D3 to D12, while for negative voltages, the LEDs are switched on in the opposite direction, from D12 to D3. Obviously, the negative voltage must be ‘rectified’, i.e. inverted, before the measurement. A suitable circuit for this purpose is presented in the article ‘Absolute-value meter with polarity detector’ elsewhere in this website. A set of transistor switches (MOSFETs) controls the direction in which the LEDs light. When the control voltage is high (+6V, according to the schematics, but any voltage that is at least 3V hig...

Here is the circuit of a Class B audio amplifier based on TDA1553 . TDA1553 is a monolithic audio amplifier class B, containing 2 x 22 watt amplifier in bridge configuration load attached. The amplifier operates from 12V DC and develops intentionaly for car audio applications. The IC also has a lot of good features such as short circuit protection, protection of the load dump, reverse polarity protection, speaker protection, etc. In the circuit, C5 and C4 are decoupling capacitors C3 input, while setting the delay for speaker protection. C1 and C2 are filter capacitors of the offer. Notes : Assemble the circuit on a good quality PCB. Use 12V DC for powering the circuit. The circuit can deliver 22W per channel into 4 ohm speakers. Fit the IC with a proper heat sink.

This Laser Controlled ON/OFF switch circuit is built around a 555 timer using very few components. Since the circuit is very simple, even a novice can easily build it and use it as a controlling device. A laser pointer, now easily available in the market, can be used to operate this device. This circuit has been tested in operational conditions from a distance of 500 meters and was found to work satisfactorily,though it can be controlled from still longer distances. . Laser Controlled ON/OFF switch Circuit diagram : Laser Controlled ON/OFF Switch Circuit Diagram Aiming (aligning) the laser beam exactly on to the LDR is a practical problem. The circuit is very useful in switching on/off a fan at night without getting off the bed. It can also be used for controlling a variety of other devices like radio or music system. The limitation is that the circuit is operational only in dark or dull lit environments. By focusing the laser beam on LDR1 the connected gadget can be activated throug...

I have a couple of front door LED lights which I would like to switch on automatically during the evening/night. The two conventional methods that are commonly available had their disadvantages: A timer switch is the easiest and cheapest solution, but doesn’t take into account day light savings. Besides that, in Einhoven, the Netherlands where I live in december the sun sets around 16:30 while in June it doesn’t get dark before 22:00. A simple timer doesn’t take that into account either. Since you only want the lights on when it gets dark, instead of time you can also use a light sensor to distinguish day and night. You have these front door lights that have this built in. The problem that I had with these devices is that they start bouncing (‘flickering’) around sunset/sunrise. They constantly turn on/off which causes damage to the LED lights I was using. This cost me already several expensive led lights. [ ]