I built an LCD oscilloscope module using the JYE Tech 062 digital storage oscilloscope purchased from NKC Electronics.  I  purchased the kit so the LCD would be unattached.  The kit has all the SMT parts soldered so you only need to add the thru-hole components.  I mounted the LCD above the PCB which I rotated to fit in a 2U panel.

Construction

I did not implement the reference signal, external trigger, or the RS-232 interface on the module.  I did add J5 to the PCB so I could access these features.

The LCD oscilloscope is designed for 9 to 12 volts AC.  I eliminated the rectifier diodes and added a 0.1" MTA connector for 10 volt DC power.  I designed an auxiliary PCB to mount on the rear of the LCD to regulate +15 volts to +10 volts.  Using a 10 volt regulator splits the heat dissipation with the +5 volt regulator on the LCD oscilloscope.

DJB-019 Power supply schematics  updated

The LCD oscilloscope draws 110 mA from the +10 volts supply without the backlight.  The backlight is normally wired to the +5 volt regulator and draws an additional 100 mA.  I wired the backlight to the auxiliary PCB and added a series resistor to reduce the current but still provide reasonable brightness.  Jumpers on the auxiliary PCB select either +15 volt only, or +5 and +15 volt operation.

The frequency input is limited to 0 to 5 volts. I cut the frequency run on the PCB after the switch and added a 10K series resistor with a schottky diode to limit the negative voltage and a 5V zener diode to limit the positive voltage.

The input signal (yellow) is limited to -0.3 to +5 volts for the frequency circuitry.

Operation

The LCD is a nice display. The LCD oscilloscope has a 1V/div that you can multiply by 1, 2, or 5. The  2V/div fills the screen nicely with a 10V pk-pk signal.

The scope triggering works well if you have a repetitive waveform. The display will jump around quite a bit if the waveform is non-repetitive.  You can hold the display and see the waveform and the oscilloscope has a larger sample buffer than the display so you can scroll horizontally through the waveform.  The trigger point is at 25% of the acquisition buffer.

There are three operating modes:

1. SIG records one acquisition buffer and updates and holds the display.

2. NOR updates the display when it has a valid trigger (and so will display the last acquired waveform if it does not have a trigger).

3. AUT updates the display continuously.

The + and - buttons (INC and DEC on my module) seem backwards in some modes but is easy to figure out by watching what is happening.

I am unable to get any kind of useful display on the 2 µS horizontal scale.  The 5 µS provides a good image and provides a readable waveform up to ~100 KHz.  You can see increased leading edge rounding due to the capacitive loading when using a 1X probe.  A lower capacitance 10X probe improves the leading edge nicely and extends the useful range to ~150 KHz. The lower waveform is from my Tek oscilloscope with a 1X probe daisy-chained from the front panel jacks.

The frequency mode is very useful for tuning VOCs but remember the input voltage is limited to 0 to 5 volts. I modified my circuit to keep the input voltage within this range.  When you press the OK button for 3 seconds to exit frequency mode, it sometimes takes a second or so to return to the oscilloscope display.

There is a Google JYE Tech LCD oscilloscope group which is quite active and they post information on updates to the firmware.

There are also couple of videos on youtube that show the JYE Tech LCD oscilloscope

     Video 1  Displaying a waveform and frequency measurement.

     Video 2  Displaying various waveforms from a Noiz Box.

Firmware Updates and PC Interface

Using the boot loader to update the firmware is quite easy and JYE Tech provides good documentation on how to use the boot loader and the AVRubd program with a serial interface.  JYE Tech provides schematics for a TTL to RS-232 level interface but I chose to use a Max232 which required fewer parts.  I verified the serial interface by uploading this screen capture from the LCD oscilloscope.

DJB-019 Serial interface schematic

Firmware level -091 resolves the issue of changing from SIG mode as mentioned in the video. 

Firmware level -092 adds trigger output to cascade multiple scopes for multi-channel display.

Firmware level -100 adds FFT functionality.  This screen image shows the FFT of a 500 Hz square wave at 500 Hz/division.  You can see the fundamental at the first division and the odd harmonics at diminishing amplitude at the 3rd, 5th, 7th, and 9th division.

Panel

I used RUN, INC and DEC on my panel instead of OK, + and -.  The on-screen menus refer to OK, + and - so I changed RUN to OK on the FrontPanelExpress design files.

I was surprised when my panel did not have the legends filled.  I learned that there is an "in-fill engravings" box which must be checked on the panel properties.  I updated the design files and used a white Artist's Oilbar paint stick to fill my engravings.

The front panel thickness is limited to about 2 mm due to the thickness of the push buttons.  This is a standard 3 mm panel with an expensive 1 mm cavity milled in the back for the PCB to fit into.

DJB-019 LCD 3mm Oscilloscope FrontpanelExpress design file  not built or verified

This is a 2 mm panel design which is much less expensive.  I used 1 mm #8 plastic washers (Mouser 561-D832B) glued on the back at each of the four mounting holes to keep the module flush with adjacent panels.  I moved the three slide switches up 0.25 mm from my panel as they were a bit low (I have verified this change only by a visual comparison of a print of the panel to the PCB).

DJB-019 LCD 2mm Oscilloscope FrontpanelExpress design file  updated

Other Modifications

Here's some other modifications that could be made to this module.

1. Inputs:  You could change the four jacks from a multiple to separate inputs for DC, AC, frequency, and external trigger.  You would eliminate the AC-DC-Freq switch and wire the connections to each jack .  The AC capacitor would go between the AC and DC jack and the frequency input protection components would be mounted on the jack (much easier than modifying the PCB).
2. Reference: You could a jack for the 500 Hz reference signal.
3. RS-232: You could add a front panel RS-232 connector easy firmware updates and screen captures.
4. Backlight: You could add a switch with different resistor values (high,  medium, and off) for backlight brightness.
5. Legends: You could change INC and DEC to + and - to match the on-screen menus.

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