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Electronics projects

Last update: 31/07/2015

Here follows a simple and really economical 10A variable power supply (1.2-30V). An LM317 have been used to drive 3 npn TIP41C transistors (or, better, three 2N3055). Nothing to say about the project, it is really simple. The main supply must be connected to a rectified source (transformer + 25-30A bridge rectifier).

12f675 pwmTo regulate the speed of a motor trough a simple potentiometer. With a small microcontroller this job can be done quite easily.

We needed of a speed regulator to control the motor of our cnc machine (a small machine, for pcb); to achieve the result we've used a 8 pins microcontroller, a 12f675, using the analog to digital internal converter and using the pwm to drive 3 power mosfets.

This is really simple variable power supply. Using an LM317 the ps can supply upto 1.5 amp, 5amp. using an LM338. An heatsink is a must. An external rectifier (bridge) is needed. 

L293D

One of the most interesting chip for robotic projects is the L293 produced by STM and Texas. It is a simple quadruple half-H driver (only 600  ma) designed to accept standard TTL logic levels, widely used to control small dc and even stepper motors (remember that the `D` version has internal clamp diodes).

Ecco un alimentatore variabile molto semplice che fa uso di un LM317 (sino ad 1.5A) o di un LM338 (sino a 5A). Nulla da dire riguardo lo schema, molto tradizionale. Questo alimentatore utilizza un microcontrollore quale volt/amperometro. Il programma per il pic è stato studiato per rendere semplicissima la regolazione dei due trimmers per il settaggio.

relays brdThis is another board to be used in connection with a parallel port of a pc or using a microcontroller. It is a simple board-driver for 8 relays. The board is protected by optocouplers and it uses standard, very common, relays (G5LE - 10A - 220V).  

Here follows a simple count down timer useful for the production of pcbs using photoresist and UV lamps. We have used a pic 16F887 Microchip microcontroller; there are no particular reasons, we have simply used the picmicros available at the moment.

Here follows the schematic (hex and sch downloadable, as usual, in the repository).

Sometimes we need to power an electronic project (using picmicro, for instance) powering it with a voltage of 3.3 or 5V but we have a source of 1.2-2.4 V give by one or two batteries. There are two solution to this problem: increase the number of the batteries or use a particular switching IC to increase the value of the voltage.

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