We're going to do Pulse Width Modulation using a generic N-channel power MOSFET connected to the Transmit data pin from the computer's rs232 port. When the serial port is idle, the pin will sit at the '1' state, which by the time it's translated to rs232, is something like -12V (depending on drivers, it might be closer to -9V or -5V), and the transistor will be quite OFF. When we transmit '0' bits on the serial port, the rs232 pin will go to +12V or so, which is enough to turn on most mosfets pretty well. If we transmit a lot of '0' bis in a row, the motor will be close to fully ON and the motor will run fast. If we transmit mostly '1' bits, the motor will run more slowly. One way to control the motor without having to write ANY software is to prepare some files containing appropriate bytes (with more or less 0 bits), and simply COPY them to the COM port where you have the motor connected.

Multi Harga Jual (1 Harga/Harga berdasar Quantity/Harga Berdasar Level/Harga Berdasar Satuan). Item Bergambar (Gambar bisa tampil pada saat Transaksi). Item Barang Bisa menggunakan Multi Serial. Diskon Bertingkat pada Item (Dapat Setting Diskon bertingkat pada masing-masing item, Contoh diskon 10+5+2). Free software program kasir.

I prepared several files (using emacs, but whatever works for you is fine): • 0.pwm:: contains 5000 NULL characters (control-space on most keyboards)[br] This is about as close to 'full speed' as we'll be able to get with this technique. • 1.pwm:: contains 5000 control-A characters (ascii 01) (one '1' bit per char) • 3.pwm:: contains 5000 control-C characters (ascii 03) (two '1' bits per char) • 7.pwm:: contains 5000 control-G characters (ascii 07) (three '1' bits per char) • 15.pwm:: contains 5000 control-O characters (ascii 15) (four '1' bits per char) • 31.pwm:: contains 5000 control-_ characters (ascii 31) (five '1' bits per char) • 63.pwm:: contains 5000 '?' Characters (ascii 63) (six '1' bits per character) • 127.pwm:: contains 5000 DEL characters (ascii 127) (seven '1' bits per character) (Now that I've drawn pictures, you'll notice that the actual bit patterns aren't ideal. Since rs232 serial transmits LSB first, we really want to shift in zeros instead of ones.