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Old 28th September 2006, 08:38 PM   #1
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Default 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.
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Old 28th September 2006, 08:43 PM   #2
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maybe sn75176 ?
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Old 7th October 2006, 02:13 PM   #3
RussB is offline RussB  United Kingdom
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No need to bother with a chip, a resistor & zener diode should do the trick
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Old 7th October 2006, 03:19 PM   #4
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"RussB" How can you be soo sure ..without knowing the load current ?
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Old 7th October 2006, 03:26 PM   #5
peufeu is offline peufeu  France
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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.
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Old 7th October 2006, 08:13 PM   #6
RussB is offline RussB  United Kingdom
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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
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Old 7th October 2006, 08:34 PM   #7
poobah is offline poobah  United States
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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.


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Old 8th October 2006, 03:21 AM   #8
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RussB wrote:
Quote:
Hey, I just registered, be gentle!
then change your "Biography"...you'r not as mentioned..
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Old 8th October 2006, 06:39 AM   #9
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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

Why writing being an idiot and have no interests
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Old 8th October 2006, 12:54 PM   #10
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Real interests changed....free samples
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