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-   -   12v to ttl converter (http://www.diyaudio.com/forums/everything-else/87327-12v-ttl-converter.html)

xplod1236 28th September 2006 08:38 PM

12v to ttl converter
 
I need help finding a chip that converts 12v levels to ttl. This will be used in a car, so a resistor divider will give me changing levels depending on if the engine is running or not.

darkfenriz 28th September 2006 08:43 PM

maybe sn75176 ?

RussB 7th October 2006 02:13 PM

2 Attachment(s)
No need to bother with a chip, a resistor & zener diode should do the trick

sivan_and 7th October 2006 03:19 PM

"RussB" How can you be soo sure ..without knowing the load current ?

peufeu 7th October 2006 03:26 PM

There are a lot of possibilities :

- resistor + zener diode (as above)
- use a transistor as an open collector (inverts the signal)
- 1Meg resistor and trust the IC's internal clamping diodes (haha)
- the professional solution : use a specialized IC from Max Semi (don't remember the part number right now)

If you want ot do it the other way (ie TTL -> 12V) the open collector is the simplest.

RussB 7th October 2006 08:13 PM

Quote:

Originally posted by sivan_and
"RussB" How can you be soo sure ..without knowing the load current ?
Hi SivanandBalan,

The clue was in the question "ttl". However, if people ask the wrong question, they'll get the wrong answer.

Sure, it wasn't an optimised solution, more information would be needed for that. This requirement needs a passive solution, active solutions will need their own supplies, packaging and so on. Sledgehammer/walnut?

Hey, I just registered, be gentle!

Russ

poobah 7th October 2006 08:34 PM

google "logic level translater" or "logic level shifter"

Do keep in mind that automobiles have a side effect known as "load dump". For a brief period when the ignition is shut off, a pulse of 60 to 400 Volts blasts through the 12 Volt bus. Not a huge problem, but just be sure you have some series resistance in your inputs to limit currents that flow through the protective diodes in your chips.


:)

sivan_and 8th October 2006 03:21 AM

RussB wrote:
Quote:

Hey, I just registered, be gentle!
then change your "Biography"...you'r not as mentioned..:cool:

peranders 8th October 2006 06:39 AM

Quote:

Originally posted by RussB


Hi SivanandBalan,

The clue was in the question "ttl". However, if people ask the wrong question, they'll get the wrong answer.

Sure, it wasn't an optimised solution, more information would be needed for that. This requirement needs a passive solution, active solutions will need their own supplies, packaging and so on. Sledgehammer/walnut?

Hey, I just registered, be gentle!

Russ

TTL means in this case Transistor-Transistor-Logic. Check parts like 74xx, 74LSxx etc.

"1" > 1.4 volts

"0" < 0.7 volts

:scratch: Why writing being an idiot and have no interests

sivan_and 8th October 2006 12:54 PM

Real interests changed....free samples:D


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