Simple AVR-Transistor and components on ATmega8 (88)

Simple AVR-Transistortester on ATmega8 (88)

On one of the sites I found an article where they offer to assemble a simple semiconductor probe tester called the AVR-Transistortester. Studying this topic, I found that the AVR-Transistortester made almost all the same differences only in the microcontrollers and displays used. The simplest circuit on the ATmega8 can also be used with the ATmega48, it contains all the necessary minimum parts, which will not be difficult for a novice radio amateur to assemble.

 

Types of tested parts:
(item name - indication on display):

• - NPN transistors - on display "NPN"
• - PNP transistors - on display "PNP"
• - N-channel-enriched MOSFETs - on display "NE-MOS"
• - P-channel - enriched MOSFET - on display "PE-MOS"
• - N - channel-depleted MOSFET - on display "ND-MOS"
• - P-channel-depleted MOSFET - on display "PD-MOS"
• - N-channel JFET - on display " N-JFET "
• - P-channel JFETs - on the display" P-JFET "
• - Thyristors - on the display" Thyristor "
• - Triacs - on the display" TRIAC "
• - Diodes - on the display" Diode "
• - Two-cathode diode assemblies - on the display" Dv diode CA "
• - Two-anode diode assemblies - on the display "Two diode CC"
• - Two diodes connected in series - on the display "2 diodes serial."
• - Symmetrical diodes - "2 opposite diodes" on the display
• - Resistors - range from 1 Ohm to 10 MΩ [Ohm, KOhm]
• - Capacitors - range from 0.2nF to 5000uF [nF, uF]
• Description of additional measurement parameters:
• - H21e (current gain) - range up to 1000
• - (1-2-3) - order of connected element terminals
• - Availability of protection elements - diode - "Diode symbol"
• - Forward voltage - Uf [mV]
• - Opening voltage (for MOSFET) - Vt [mV]
• - Gate capacitance (for MOSFET) - C = [nF]

Traditionally for myself, I redrawn the circuit in DeepTrace and spread the board for my components. I used a planar microcircuit with thirty-two pins.

 

The schematic diagram.

 

PCB Placement parts

 

I tried to separate the board so that all the details were under the display, and the test panel, button and control LED were in front of the display. I used a standard power connector for connecting any adapter up to 15V, this does not affect the accuracy of the readings.

 

With regards to the parts used.
Transistors VT1-VT3 any low-power corresponding to the transition.
Resistors are also any, of any accuracy class except R7-R12, the main thing is that their resistance does not differ much from the required ones. It is very important that resistors R7-R12 are of a higher accuracy class. If you don't have any, then you need to arm yourself with a good, accurate tester and select resistors R7-R12, with a minimum error.
The accuracy of the readings depends on this. The device, correctly assembled from working parts, does not need adjustment. It works immediately, transistors and other parts besides high-capacity capacitors are tested quickly enough.

I program such microcircuits, already soldered into the board.

 

Micro-controller programming

I solder the wires to the tracks leading to the corresponding conclusions. And then I solder the rest of the details. It can be programmed even after the final assembly of the device.

And which programmer, or which program to use is already a matter of taste. I liked the AVRDUDE program so much.

The main thing is to install the correct fuses.

For ATmega8: lfuse = 0xc1; hfuse = 0xd9
For ATmega48: lfuse = 0x42; hfuse = 0xdf; efuse = 0xff

In the archive I post all my and not my materials for the manufacture of this device.

Also in the archive, there is a firmware for the russification of the instrument readings (English and Russian EEPROM, correct display in Cyrillic µ and Omega), this is if your display supports Russian characters. Unfortunately, my display was not one of those.

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