12v to ttl converter

xplod1236 · 28th September 2006, 08:38 PM

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

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..

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

Why writing being an idiot and have no interests

sivan_and · 8th October 2006, 12:54 PM

Real interests changed....free samples

28th September 2006, 08:38 PM	#1
xplod1236 diyAudio Member Join Date: Dec 2003 Location: On the couch	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.

7th October 2006, 03:19 PM	#4
sivan_and diyAudio Member Join Date: Dec 2004 Location: Dxb / India	"RussB" How can you be soo sure ..without knowing the load current ? __________________ SivanandBalan

8th October 2006, 12:54 PM	#10
sivan_and diyAudio Member Join Date: Dec 2004 Location: Dxb / India	Real interests changed....free samples __________________ SivanandBalan

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28th September 2006, 08:43 PM	#2
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	maybe sn75176 ?

7th October 2006, 03:26 PM	#5
peufeu diyAudio Member Join Date: Mar 2001 Location: Lyon, France	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.

7th October 2006, 08:34 PM	#7
poobah diyAudio Member Join Date: Nov 2005	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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