Posted on Tuesday, April 1, 2008 • Category: Battery Chargers
The charger in this project is designed to charge two AA NiMH or NiCd cells of any capacity (as long as they are the same) at about 470mA. It will charge 700mAh NiCds in about 1.5 hours, 1500mAh NiMHs in about 3.5 hours, and 2500mAh NiMHs in about 5.5 hours. The charger incorporates an automatic charge cut-off circuit based on cell temperature, and the cells can be left in the charger indefinitely after cut-off.
Posted on Tuesday, April 1, 2008 • Category: CNC Milling Devices
Presented here is a 3-axis CNC milling device for milling small mechanic parts. It's capable of engraving and drilling PCB boards. The milling device is a stepper motor controlled x-y table, and a motorized (z-axis) stand for a 'Dremel' tool.
Posted on Tuesday, April 1, 2008 • Category: RC Servo Motors
Below you find the schematics of the servo-controller I use. It is based on the PIC 16F84A from Microchip. To obtain a good resolution, I use a version of 20 MHz. It's interfacing to the serial port with a rate of 38400 baud. The PIC is controlling 12 servos in parallel with a resolution of 240 steps over 90 degrees rotation.
Posted on Tuesday, April 1, 2008 • Category: Frequency Wave Generators
Here's a universal 555 frequency generator with four frequency ranges that might be handy for building any projects that deal with frequencies. JP3 is a button used to switch the device on and off. The power supply (anything from 4-12V) is connected onto JP4. JP2 serves as the output for the signal with an attenuator, if we don't need the full strength (voltage) of the signal, only, say 3V of 5V. We can set the output value by R2. JP1 gives the full strength of the signal, with a current depending on the 555 type you use. R3 is used to set the frequency within a range chosen by the DIP switch S1. You can set which range of frequencies you want to use with a DIP switch. With it you enable or disable a capacitor which is hooked up into the datasheet circuit of the 555 chip.
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