Digital

AVR LCD Microcontrolled Oscilloscope circuit

A few months ago as I was surfing on the net, I saw an oscilloscope based on PIC18F2550 microcontroller and a KS0108 controller based graphical LCD. That was Steven Cholewiak’s web site. I had never seen before so amazing microcontroller-only oscilloscope. That was realy impressive circuit, so I decided to design something like that but in C language instead of assembly that I was using all those years. The best solution for me was the WinAVR as it bases on open source AVR-GNU compiler and it works perfect with AVR studio 4. The graphics library that I used, is made by me specific for this project. It’s not for general use. If you want to include it to your codes, you have to convet it as you need to.
The maximum signal speed who can show up this oscilloscope is 5 kHz in square signal. For other signals (sine or triangle) the frequency is lower ( almost 1 kHz) for having clear view of the signal. Description The operating voltage of the circuit is 12V DC. By this voltage, the power supply is producing 2 voltages. +8.2V for IC1 and +5V for IC2 and IC3. This circuit can measure from +2.5V to -2.5V or from 0 to +5V dependent by S1 position (AC or DC input). By using probe with 1:10 division you can measure almost 10 times higher voltages. Moreover, with S2 you can make an extra division by 2 the input voltage. Programming The ATmega32 Burn the ATmega32 with AVR_oscilloscope.hex and select external crystal at the fuses section. After that, you Must disable the JTAG interface from your ATmega32 microController. If you don’t do that, the mega32 will show you the initial screen and when it go to the oscilloscope screen it will restart immediately to the initial screen and it will stay there for ever. Calibrations The only 2 things you have to calibrate is the LCD contrast trimmer P2 and the P1, to move the beam at the center of the LCD. To do that, apply only the power supply to the circuit and adjust the P2 up to the point you will see clear the appeared pixels on the screen. Then, adjust the P1 up to the point the beam is moved at the middle of the LCD (at the horizontal line of the cross). Usage You can move the beam up or down the screen by pressing… http://www.serasidis.gr/circuits/AVR_oscilloscope/avr_oscilloscope.htm
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99 mV to 999 mV meter schematic by CA3161-CA3162

This circuit can for example be incorporated into a diet to pressure warning. The meter can measure voltages from -99 mV to 999 mV. The circuit uses two ICs, the CA 3161 and CA 3162. IC1 converts the analog signal into a digital signal. IC1 is also the multiplexed signal to T1-T3 can be controlled. The BCD code is then fed to IC1 IC2, a BCD/7-segments converter. Then the signal is fed to the displays. Pin 6 of IC1 (hold) can be used for a number of things. When pin 6 is grounded or open, the 4 Hz sampling frequency. When pin 6 is at 1.2 V, then enter the HOLD function is activated.
The output will remain unchanged, so the display is put down. If pin 6 is at 5 V, the sampling frequency 96 Hz. Adjusting the meter is through the HI and LO inputs to GND. P1 is then adjusted so that the display “000″ indicates. Then a known voltage from 0 to 1 V is connected to HI and LO (LO to GND). The display then P2 so cut that regulates the voltage in mV is indicated. With voltage dividers, the range can be increased. The points of the displays can be used by dp 1, 2 and / or 3 to GND. R1-R3 = 220 ? P1 = 10 kOhm 10 or 15-turn trimming potentiometer P2 = 5 kOhm 10 or 15-turn trimming potentiometer C1 = 270 nF T1-T3 = 636 BC IC1 = CA 3162 IC2 = CA 3161 LD1-LD3 = 7-segment LED display common anode http://www.circuitsonline.net/schakelingen/60/meten-en-testen/3-digit-dvm.html

Digital counter circuit

With this counter you can count laps for example (in conjunction with the Simple light trap ). The circuit uses two TTL ICs 74LSxx the series. The left IC is a decimaalteller. The input pulses 14 are counted and converted to the corresponding BCD code. This code is passed to the second IC, which is a code converter and display driver. Here the BCD code correct the display driver for LD1.
The counter can be any TTL signal is sent (eg with the printer port). The signal must not exceed 5 volts. R1-R7 = 220 ? LD1 = 7 segment LED display (common anode) IC1 = 74LS90 IC2 = 74LS247 http://www.circuitsonline.net/schakelingen/21/meten-en-testen/digitale-teller.html