AVR-Transistor Tester

[FOOKz™]

AVR-Transistor Tester

Parts List:

R1, R3, R5	680 OHMS
R2, R4, R6	470K OHMS
R11, R13	10K OHMS
R12	3K OHMS
R14	1K OHMS
C1, C3	100nF
IC1	ATMEGA8-P
IC2	LM7805
DIS1	HD44780
S1	Tact Button
S2	SPST on/off switch

This is a thread for anyone who wants to build one from scratch maybe we can convince the rest of the staff to sell this as a kit since this can replace 100's of dollars worth of equipment.


Original site: http://www.mikrocontroller.net/articles/AVR-Transistortester

hyper999, Mogler, Famas, frenulem and I are going to build one of these.

Video Demonstration

Showing off the semiconductor tester, great AVR project from Markus.

Schematic Diagram

Work Log

Working on PCB Design

[hyper999]

built it, seems to work, but im gonna need to edit  the code as the on screen messages are in german now i just need the pcb layout

EDIT: it seems to be detecting all resistors as paralell opposite diodes, this could be due to my wiring or because the youtube video above has different software on the AVR (mines in german theres is english), or because i had to bodge some resistors, i dont know

EDIT2: Just found some updated designs and software here, http://svn.coremelt.net/avr/semiconductor_tester/

EDIT3: Ok sorted now, english, resistors working, caps working, transistors working, diodes working, uart output now included and working. cant test accuracy until i get the right resistors though. also the uart means you can use a cheap serial>usb cable instead of or as well as an lcd

there is also updated schematics including one that sacrifices the auto turn off but reduces the part count a bit

also fookz if its not too much trouble could you add to the pcb a connection for uart (pin 26 for tx and gnd) and a 6pin isp header? or gimme the files so i can try add these myself?

[FOOKz™]

there is also updated schematics including one that sacrifices the auto turn off but reduces the part count a bit

O_o

Which schematic is it? I just got home and is working on the PCB layout for the schematic posted above right as we speak.

If there are major changed to the board I may have to redo, I think its going to be fairly easy to change anyways.

[hyper999]

extra schematics

a connection from pin 26 needs to be added to all for uart though

[FOOKz™]

Look at the 7085 5volt regulator.

The pinouts are ether wrong or it's specific to the part.

I've looked at the diagram and realize that the schematic does not call for the typical 7805 TO-220 package. The PCB design is based upon the LM78M05 from National Semiconductor.


EDIT: I have attached the current beta PCB Layout.
The image is off-scale, so don't waste your time building one yet. The layout is huge! theres more room to make it smaller; its just going to take some time to get it down to size.

I will include two PCB designs:
1. a layout that is now wider than the width of 2 ICs placed side by side
2. a layout for general purpose project enclosures (larger than the 1st)

[hyper999]

heres a pic of my breadboarded setup;

[Famas]

i really want to make this

[FOOKz™]

So Far this is what the beta version of the PCB looks like.

@Hyper please double check my work make sure that everything fits correctly before printing to your transfer paper just make changes as needed a repost the cad file.

@Famas maybe we can get kits to be sold in the AM Shop

Surface mount layout to come soon then I will post my work log.

[hyper999]

ok decided that im gonna need my own PCB if its gonna fit in my enclosure properly so here is my progress
Post Merge: February 01, 2011, 05:51:46 AMok here is the finished design, if you spot any differences betwwen the schematic and the PCB let me know (known differences; some resistors have been rounded to 30k, lcd power connections added.)

[Famas]

been looking hard hyper and looks perfect other than this ringed the red connector circle doesnt look to be touching the green line

[hyper999]

yeah dw bout that it is connected i just rechecked

[hyper999]

ok built this all up thursday and it didnt work, so theres something wrong with my pcb layout i think. also i think the bc557 has blown up but i havent had time to check things ouyt properly.

also should the 7805 heat up really quickly if i short the emitter and collector of the bc557?

[FOOKz™]

no the 7085 wont heat up. actually you don't need the 'T3' BC557 and R10. Change R7 to 500 Ohms and connect it to +9v (pin3 to the 7805).

Breadboard it first.

the bc557 is probably dead because its handling the entire load of the whole circuit.

[hyper999]

if i do like you said and remove T3 and R10 wont that kill the auto off functionality?

P.S would you mind explaining to me how the auto on off works?

[FOOKz™]

oh wait thats the auto off transistor? lol woops then scratch what i said earlier now since i get why that transistor is there... Just replace T3 with a better transistor that will handle more current. possibly a 2N3906 ??

P.S would you mind explaining to me how the auto on off works?

I think that the auto off feature works by making pin 12 Low which turns off T1 and LED1, then more current is directed to T3 which turn it on thus switching power off of the entire circuit. When S1 is pressed it turns the chip back on making pin 12 High again which wakes up the circuit so you can test whatever you need.

[hyper999]

but i know the BC557 will work for t3 as i built this on my breadboard before i made the pcb but i think i put some wrong traces on my pcb causing a short somewhere or something.

[Famas]

i want to make this hyper

[hyper999]

i know you do but you also want a pcb and i dont have a working one right now
Post Merge: February 07, 2011, 01:56:33 PMok ive ordered a shed load of transistors so they should be here in a couple of days then i can start debugging. any tips fookz?

[FOOKz™]

but i know the BC557 will work for t3 as i built this on my breadboard before i made the pcb but i think i put some wrong traces on my pcb causing a short somewhere or something.

idk its a possibility I can't really help you 100% because im not physically with you to see the board. well maybe if you could take a photo of what you have so far

With the transistors i don't know what else to say except to know that the BC557 and the 2N3906 series PNP transistors are almost exactly the same and are 100% interchangeable with any other NPN/PNP complimentary transistors (as long as they are wired & operate correctly) in this case.

Double check, triple check!

Also I won't be having lots of free time anymore because my work hours switched earlier and i need to get to bed earlier (im tired as balls atm).. so ya. I probably could design and etch a surface mount version and fit it within a calculator case?

[frenulem - No.5417]

I probably could design and etch a surface mount version and fit it within a calculator case?

As twist would say, I want it.

[frenulem - No.5417]

Can you really fit it inside the calculator?

[FOOKz™]

Yeah you probably could because its all surface mount... just get 4 of those 1.5v button cell batteries that add up to 6v then regulate it to 5v using that 7085 (surface mount version)... remove a few of the calculator's buttons (leave a few for on/off test etc..), bondo, sand, n paint the unused button holes, then add all the crap in there hook it up where the screen would be and make sure it all fits.

[frenulem - No.5417]

damn that'd be usefull, lets see hyper whack this one up and then we can go from his schematics

[FOOKz™]

Realistically all the hard work is done for anyone who wants to build it; we just have to get a finalized PCB design & parts list for a possibility of kits being sold in the Acid mods shop for a nice price.

good DMM meters with a good transistor tester sell around $80 +
the best testing equipment that does the same as this device is around $300 +

This device competes with it so ya you'll be saving tons of green.

Edit: this is the calculator I am planning putting the SMD version of the PCB. I think it will fit.

Also @hyper if the price isn't too high I want to buy a pre-programmed chip off of you, ill pay shipping&price.

[frenulem - No.5417]

Also @hyper if the price isn't too high I want to buy a pre-programmed chip off of you, ill pay shipping&price.

yeah i wanna do the same, he said £2.50 of the chip and p&p will cost More than that, not much more, dunno the prices to the us tho

[hyper999]

yeah fookz thats cool not sure where i would get a smd atmega from over here though, seeing as your all the way over in the us you may be better off building a programmer like this; http://electronics-diy.com/avr_programmer.php
Post Merge: February 07, 2011, 06:57:40 AMok PCB v2 done.
- sorted out error with LCD connections
- some component relocations although space is really really tight

still cant work out what wen so wrong with v1 though :/
@fookz could it be that i used electrolytic caps instead of ceramic disk? just a thought oh and i have ordered some more ceramic ones with my transistors so v2 will sort that

oh and awseome pcb making tip, got through the schematic highlighting conections as you make them.
Post Merge: February 08, 2011, 04:25:38 PMok parts here, let the dubugging begin! lol

also noticed there is something missing from the schematic there should be a 0.22uF cap between Vi and GND of the 7805, i only have a 0.1uF but i think it will be fine.
Post Merge: February 09, 2011, 01:50:08 AMok set everything up started probing with my multimeter and found some odd voltages, anyone know what might cause the 7805 or the bc557 to act like this?

p.s i also have checked all components still function correctly outside of the circuit

[frenulem - No.5417]

right, If you can grab a small knife or scapel, go inbetween the tracks to mack sure no bridges have been made, im sure theres no obvious ones but to double check

ok, go over

Transistors
ICs
Cap values
Res values

I'm looking over the PCB layout but its hard cuz i feel like throwing up right now

[hyper999]

done all of that think im gonna start cutting traces and continuity testing to speed things up as im gonna have to remake this pcb anyway
Post Merge: February 09, 2011, 05:15:32 AMOk pretty sure the problem is that the bc557 is not putting through enough voltage, what might cause this?
Post Merge: February 10, 2011, 11:45:37 AMok i am getting 5v now but now when i tap the button the lcd baclight turns on when the button is pressed and then the led blinks on dimly for a slpit sec after the button is released when i press and hold the button for like a szecond sometimes the led and backlight come on a then go off after a while and sometimes they just stay on till i disconnect the battery. any ideas?

[FOOKz™]

ok i am getting 5v now but now when i tap the button the lcd baclight turns on when the button is pressed and then the led blinks on dimly for a slpit sec after the button is released when i press and hold the button for like a szecond sometimes the led and backlight come on a then go off after a while and sometimes they just stay on till i disconnect the battery. any ideas?

whip out the good old volt meter to check for any error with a capacitor... idk thats all i can think of.

OK hyper when you get those AVR chips i hope you can figure out how to program the surface mount ones. I'll pay for the shipping and stuff.

check to make sure the external clock is working right.

[hyper999]

ok i can get them smd ones (although they are twice the price of the same but through hole) how many would you want?
altough it may be cheaper quicker for you to just use one of these if you have a serial port
http://electronics-diy.com/avr_programmer.php

what do you mean by checking the external clock tho?

also how would i check capacitors?