Introduction: Digital Oscilloscope With LCD Screen
I tried to make simple and cheap oscilloscope using common parts from today's component retailers. When creating, I tried to reduce the number of parts, while maintaining the minimum necessary for the functionality of an oscilloscope - for different settings and troubleshooting of power converters , household appliances control circuits , for the study of different devices, where not required accurate measurements and high frequencies , and you just need to look at the waveform , up to 200 ... 300kHz.
- Single channel
- Maximum sample frequency: 4MSPS
- Time base: 4us/div, 10us/div, 20us/div, 50us/div, 0.1ms/div/, 0.2ms/div, 0.5ms/div,
1ms/div, 2ms/div,5ms/div, 10ms/div, 20ms/div, 100ms/div, 200ms/div, 500ms/div
- Sensitivity: 0.1V/div, 0.2V/div, 0.5V/div, 1V/div, 2V/div, 5V/div, 10V/div, 20V/div
- Display resolution: 128 x 64 total, trace resolution 96 x 64
- Power supply: 2 x 3,6V Li-Ion batteries or DC adapter 9V...15V
- Current consumption ~ 90mA
- Triggering by rising or falling edge
- With grid or no grid
- You can save time base and sensitivity adjustments for next time when turn it on
Step 1: Schematic and Parts
The main part is PIC16F1827 micro controller running at 32MHz (8MHz quartz X 4 PLL).
The display is QC12864B - 128 by 64 pixels graphic LCD connected in serial mode. It utilizes an ST7920 controller chipset. Information about it here.
Тo achieve higher sampling rate is used external ADC - TDA8703 - 8 bit with parallel output. It runs at 4MHz - this is the highest speed at which this micro controller can read data.
The input circuit is a divider switched by transistors BS170, controlled by shift register 74HC595N (micro controller do not have enough pins). TL082P is used to amplify and vertical trace shift (offset). This op amp is very slow and not suitable for pulses above 5...6 kHz but I did not have noting better. If you make it please use something like AD823 or OPA2350.
The negative voltage needed for the op amp is obtained using ICL7660A integrated circuit from Intersil.
Step 2: Construction
The PCB is organized as two separate boards: the main board (70mm x 100 mm) and the keyboard. Both of them are designed as single side boards, easy to manufacture using amateur methods. Because of the routing constraints derived from single side routing, a few of the connections must be soldered as "air wires".