M328 transistor tester

Release Notes:

【Updated on 2019/11/30】

• Added patch component test socket, which can be used when there is no shell.
• Updated the links of all components in the Lichuang Mall. Now you can directly use the BOM order function of Lichuang EDA to purchase the required components in the mall. Except for the locking seat and keycaps, all other components have been matched correctly.

Based on the secondary development of the German open source project AVR Transistor Tester.

The PCB and housing were designed based on the original project.

Original project address: https://www.mikrocontroller.net/articles/AVR-Transistortester

The transistor tester is a very practical small tool. It was first developed based on atmel ATMega8 and has been upgraded to ATMega328P. It can fully automatically measure resistance, capacitance, and inductance. For inductance and capacitance, it can also test the equivalent series resistance (ESR). In addition, it can automatically identify diodes, BJTs, MOSFETs and other components and measure their related properties. All these operations only require simply connecting the component to the test socket, and there is no need to even distinguish the pin order. The tester can automatically distinguish them and identify the order of the pins.

EEVBLOG’s review of the Chinese version sold by Lopz , the UP master of Station B : https://www.bilibili.com/video/av37943758

Front view of the new version without shell:

The rear view of the new version without the casing:

Detailed production tutorial (the tutorial is based on the old version with shell):

First, send the PCB file to Jialichuang for proofing, and get the PCB as follows:

Weld the components according to the schematic diagram and bill of materials (BOM):

Prepare an LCD screen and choose the most common 1602 display screen

Solder the LCD pin header

Finally, weld the LCD to the board, be careful not to tilt it, otherwise the finished product will not look good.

Prepare an AVR downloader. If you don’t have one, it’s not expensive to buy one. When buying, be sure to ask the store whether it supports the ATmega328P chip. Because some older versions are not supported.

Connect the AVR downloader to the PCB according to the silk screen on the board, and then connect the downloader to the computer.

After connecting to the computer, open the PROG ISP software (this software is usually given when you buy a programmer), select ATmega328P in the microcontroller model selection in the upper left corner, and then click on the fuse data on the right

Edit the fuse data as low-bit F7, high-bit D9, and extended FC. This step is very important. Many tutorials on the Internet do not mention this, resulting in the finished product always having problems of one kind or another. After completing the modification, click Write.

On the main interface, click the two options of Load Flash and Load EEPROM on the right side, and select the hex and eep files in the project attachment respectively.

After both Flash and EEPROM are opened, click Automatically and wait for the burning to complete.

After burning is complete, the screen should automatically light up to indicate low battery voltage. Don't panic, this is because we haven't connected the battery at all, and the voltage measured at this time is the USB power supply voltage. Of course, the power supply for the 9V battery is insufficient. As long as the text can be displayed, it means that the production has been successful! If no text is displayed and the LCD has a white screen or a few small squares, it may be that the LCD bias voltage is not set correctly. Take a screwdriver and slowly adjust the potentiometer behind the PCB until the display can display normally.

Next, assemble the shell and print the shell parts with a 3D printer. Students who do not have a 3D printer can skip these steps and just look at the calibration at the bottom.

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Prepare four 10mm double-pass copper pillars, 2 M3 nuts, 4 M3*5 screws, 2 M3*15 screws, and 4 M3*12 screws (don’t look at the picture for this, the picture is not accurate, I took it casually of)

Prepare a battery buckle for a 9V battery (students who want to switch to lithium batteries can skip this step)

Pass through the small hole under the battery compartment and solder it to the power supply terminal on the PCB

Put the PCB into the case, take the battery and test it first, OK! no problem.

Fix the copper pillar to the panel with 4 M3*5 screws

Put it on. Remember to put the button cap on before putting it on.

Tighten 4 M3*12 screws from the back to fix the panel and PCB

Next, insert the nut into the slot behind the battery compartment. This requires a little force. It is best to smash it with something.

Close the battery compartment cover from the front and tighten the screws.

You're done! However, we still need to calibrate it before normal use, otherwise the error will be large. For calibration, you need to prepare a 1uF and 22nF capacitor in advance, and a homemade short-circuit pin (try to use pure copper with a low resistivity).

The configuration of the locking seat: the three groups on the left are test holes No. 1, the group in the middle is No. 2, and the three groups on the right are No. 3. We connect the short-circuit pins to the test holes 1-2-3 at the same time, and then press the button to turn on the phone. Wait for the screen to display "selftest mode ?", press the button briefly

When the following content is displayed, remove the short-circuit cap and the program will automatically continue calibration.

When the following content is displayed, connect a 1uF capacitor to the test holes 1-3 and remove it after the test results are stable.

While waiting for the following content to be displayed, connect a 22nF capacitor to the test holes 1-3 and remove it after the test results are stable.

Continue to wait, and soon the screen will display "test end". At this point, the calibration has been completed and you can use it happily.

Just find a 100uF capacitor and plug it in, click the button to test, the accuracy is pretty good.

To test the two-pin components, you can insert any two of the 1-2-3 holes at will. All the 3-pin components must be connected. Also note that the capacitor must be discharged before testing, otherwise the tester may be damaged.

Test inductor

The transistor can give the pin arrangement sequence and B value

Resistors are naturally stress-free

There is no problem with the unpopular dual diode

This transistor tester can not only test components, but also has more interesting functions, such as this PWM generator.

The way to enter the menu is to turn on the computer without connecting the components. When the following "No Unknown or damaged part" is displayed, press and hold the button until you enter the menu.

At this point, the tutorial is over. For more parameters and usage instructions, please refer to the documentation in the original project address. I wish you all a happy use.