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Topic: 1.8v to 5v logic level converter *solved* (Read 6237 times) previous topic - next topic

Runaway Pancake


T1 and T2 are NPN,...

Yes.

...but the transistor you showed me in the picture is, if I'm not mistaken, PNP:
http://3.bp.blogspot.com/-iTo2cABnytE/UAmCx3gD34I/AAAAAAAAFBc/_xjB__ClEuI/s1600/NPNvsPNP.png

No, Sir!
I added the inset, with the leads labelled, but the schematic's symbols remained unchanged.
http://www.jameco.com/Jameco/Products/ProdDS/178511.pdf

A test:
Disconnect "the circuit" from the RPi.
If you put the input resistor to +5 then T1's collector should be Gnd/0V and T2's collector should be +5.
If you put the input resistor to Gnd then T1's collector should be +5 and T2's collector should be Gnd/0V.

If you have access to the RPi's "1.8V", do the same using that instead +5 for the input.

I hope we have the Grounds in common: the RPi's goes to the circuit's goes to the TTL device's.  Please confirm.
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cjdelphi

what's the point of the 2nd transistor?

except increasing propergation time?

Runaway Pancake


what's the point of the 2nd transistor?
except increasing propergation time?


T1 and T2 are both inverters.
A --> /A --> A
"Hello, I must be going..."
"You gotta fight -- for your right -- to party!"
Don't react - Read.
"Who is like unto the beast? who is able to make war with him?"

schmidtbag

#18
Apr 22, 2013, 01:40 am Last Edit: Apr 22, 2013, 01:44 am by schmidtbag Reason: 1
So here's what's going on at this point:

Apparently I had the transistors in backwards, not much of a surprise since I'm pretty terrible with electronics.  Anyways, it seems to have a better end result but it's not the end result I'm looking for.  The situation is if I replace the odroid TX with the 1.8v source (also from the odroid), T2_C shows the 5v as it should - I didn't get that far before with the transistors in backwards.  However, doing this seems to make the odroid crash, as though it's draining all of it's power just for this serial port.  I am running the system in a lower power rating than recommended, but I currently have no display, no USB devices, or processor intensive tasks running.  When using the actual TX pin from odroid, the arduino doesn't seem to read it but the multimeter seems to show results.

Runaway Pancake

The "odroid" is what's represented as the RPi ?

You may benefit from a couple of new transistors. 
Tried that yet?

Please confirm.
"Hello, I must be going..."
"You gotta fight -- for your right -- to party!"
Don't react - Read.
"Who is like unto the beast? who is able to make war with him?"

schmidtbag

Yes, the odroid is represented as the RPi (but the devices have little to no relevance to each other).

I just tried some new transistors and that seems to do the trick - sending signals to the arduino seems to get me results, though I'm not sure yet if the arduino is receiving actual data or just jibberish.  I'm going to mess with it some more and see what I can get out of it.  I'll test another arduino just in case.  If both arduinos encounter problems, I'll probably be back.  Otherwise, I'll mark this as solved.

Runaway Pancake

"Hello, I must be going..."
"You gotta fight -- for your right -- to party!"
Don't react - Read.
"Who is like unto the beast? who is able to make war with him?"

schmidtbag

I used a serial to usb adapter to test this and I can confirm it is working.  And here's your karma haha.


Thanks everyone for pitching in.

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