Simple Inverter Help

Forum 2005-2010 (read only) Hardware Interfacing
1

I am lost in the simple stuff again. Could someone give me a simple sketch of how to use an npn transistor to invert a binary signal? I am trying to hook up an LCD screen and it needs inverted signal to what I get out of the TX pin...at least that's how it seems. I need it "written in crayon" almost.

I really need a basic electronics class :frowning:
I failed the only one I've ever had because I didn't like baseball enough (that's all the teacher ever talked about....nearly never heard anything about electronics)

2

http://www.kpsec.freeuk.com/trancirc.htm#inverter

3

yeah, that got me as close as anything i've found, but i'm not clear what goes where. as in which gets the TX from arduino, which goes into the RX of the LCD Serial controller, and what to do with the other side, and what resistors if any i am going to need and where.

4

Ok, I sketched my best guess based on the above link. Could someone confirm or correct it please??

Much obliged

5

That looks OK to me.

Lefty

6

If it's too complicated and it really shouldn't be, (basic elec) you can use a TTL gate 7404.

7

is the collector emitter oriented right versus the flat side of the transistor?

this is where a datasheet comes in handy, usually if its not a custom part just doing a google of "partnumber datasheet" will bring up a ton of links

in this case going though datasheetcatalog.com we get this

http://www.datasheetcatalog.org/datasheets2/12/1247641_1.pdf

that has all the stats of that part and a picture :wink:

its a rather odd critter :-?

8

Hooked up, still getting nothing much. :-?

All characters look like the same thing, which is a sorta "k" looking char.

I'm using the program from Arduino Playground - SerialLCD combined with the commands at http://www.seetron.com/bpk000_1.htm and getting the same ggibberish :frowning: i think i am gonna surrender and get different boards when i can afford them.

Any better suggestion to cheap/easy get inverted signal out from the ardu? maybe the board isn't compatable.............

9

the example code provided is sending serial out a 19,200 bits per second, the board you linked to says 2400 / 9600

change

beginSerial(19200);

in void setup()

10

Ok, I am getting a bit more progress than before, still nothing "english" from the board, but changes in the chars. I went and got a pack of NPN transistors from the only source available (Radio shack) and there are 2 types, 2222, 3904, 4401 (please suggest which is best...the datasheets don't tell me much that I can understand as a difference).
I am getting some amount of data into the board, and it is having a visible reaction, but the chars don't come up as what I expect.

i did correct the baud, before in the program, btw. But, glad it was noticed.

I don't understand why
Serial.print(254, BYTE);
Serial.print(1, BYTE);
is giving me random chars, including full dark blocks, on the screen. :-?

"RS-232 or inverted TTL, 2400/9600, N81" from the manual
And if i give it only Serial.print(254, BYTE); it'll fill the screen with solid blocks. that's about the only predictable thing it's done so far.

11

being dyslexic and code and unfamiliar territory don't mix.

9400 baud is bad too.

12

the radio shack transistors are pretty much the same aside from current handling, use a 2222 as its the most commonly used

also have you tried to send it some other values? in ascii the only values that represent English are 32-127

0-31 are control characters like space, enter and whatnot, anything above 127 is "high" or "extended" ascii and may or may not be represented, and they were never standardized fully (ie on a apple II they are used for blinking or inverse text, but on a PC it is graphical characters for text mode boxes and sudo window like screen stuff, and back to the apple II in the compact models they were used for "mouse text" to make windows and gui's)

PS: dont discount the value of a radio shack, yes they are pricey, yes their selection is only a fraction of what it used to be, but its nice to know you can go down to the mall and buy a transistor, and I still buy way too much crap there (just wish they had more like back in the day)

13

Well, it's working. At least it's displaying the text I am sending it. From here is trial and error to get it to send to the right spot, wipe it when and where i want, and display what I want. Going to try to start simple with a thermometer. I also noticed it helps to unplug when uploading code to the ardu.

Thank you all for all of the help (and PATIENCE)

14

I also noticed it helps to unplug when uploading code to the ardu.

yes the usb port goes to a usb <> TTL serial converter chip and then to the same serial port your trying to use

you might be able to use something like soft serial but 1 step at a time lol ;D

and your welcome, we were all confused noobs at one time too

15

:slight_smile: most of us get over it faster than I seem to.