74c14 substitute follow up

[yhan]

sorry for reposting. I just added some information about voltage rating
of two ICs.
----
according to [email protected] :

Yes, you can. It's the number 7414 which tells the purpose of the chip.

The C-letter means it is cmos-type (and it needs to be in your circuit,

as you mentioned), and H means it is high-speed-type. It is not
mentioned to be necessary in your circuit, but it is ok to use the
high-speed type, although not necessary.

ps. according to the datasheet, 74HC14N is Hex Inverting Schmitt
Trigger and 74C14 is Hex Schmitt Trigger.

Both ones are inverting. There are mistake, or maybe the maker of the
datasheet of the 74C14 has considered the "invertingness" a "special
feature" which wouldn't be necessary to tell on the header.

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From: Gerard Bok - view profile
Date: Tues, Mar 28 2006 5:16 am
Email: [email protected] (Gerard Bok)
Groups: sci.electronics.repair
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Yes, you can. It's the number 7414 which tells the purpose of the chip.
The C-letter means it is cmos-type (and it needs to be in your circuit,
as you mentioned), and H means it is high-speed-type. It is not
mentioned to be necessary in your circuit, but it is ok to use the
high-speed type, although not necessary.

While you are right with the 'general picture' that it is the
function that counts, you may well be wrong here

Use in a C-meter, as the poster mentioned, is likely to be
dependant on the Schmitt trigger's threshold.
And that is one of specs that varies between different
technologies


--
Kind regards,
Gerard Bok




thanks to replies. According to the datasheet the VCC of of C is higher

than HC part. In the capacitance meter i am planning to make, its
supply voltage is 12 volts but 74hc14n VCC pin max is 6 volts only.
That might be the problem. With the transistor tester using also 74c14,

its supply voltage is 6 volts. In this case, the 74hc14n might be
suited as substitute but not in the capacitance meter with the supply
voltage of 12 volts. (Because 74c14 has a Vcc ranging from 3.5-15 v but

74hc14n only up to 6 volts). Am I right?

tnx again,


ian

 

[[email protected]]

but not in the capacitance meter with the supply
voltage of 12 volts. (Because 74c14 has a Vcc ranging from 3.5-15 v but

74hc14n only up to 6 volts). Am I right?

Okhay, if that is said on the datasheet and ur circuit is using 12V,
you're right, that it is a problem, too, although you can correct it by
using a 7805 regulator to drop down the Vcc to 5V. But, the problem
that Gerard Bok mentioned refers to _threshold_ voltage. It may cause
problems if it is different, depending on the circuit. See datasheets
if the threshold voltages are mentioned there. But even if not, you can
try it if you want. But if u do, remember to use the regulation for Vcc!

 

[yhan]

thanks for the support, ill try it soon...

 

[yhan]

good day, let me ask more question please.

I have here 7805 regulator ready for use. I just dont understand if a
12 volt circuit design can be operated on 5 volts. Let me enlighten
with this thing. Can it be compatible? Is there no operating
differences or malfunction of the circuit because the circuit will
operate with lower voltage supply and that might affect the operation
because it doesn't go with the circuit design? If it is still works,
i'll be glad coz i will not bother to find 74c14 which is not available
in my place.

tnx again,

ian

 

[James Beck]

good day, let me ask more question please.

I have here 7805 regulator ready for use. I just dont understand if a
12 volt circuit design can be operated on 5 volts. Let me enlighten
with this thing. Can it be compatible? Is there no operating
differences or malfunction of the circuit because the circuit will
operate with lower voltage supply and that might affect the operation
because it doesn't go with the circuit design? If it is still works,
i'll be glad coz i will not bother to find 74c14 which is not available
in my place.

tnx again,

ian

I would stick with the original design and get the C parts. The higher
operating voltage may be needed for a particular function of the device.

Jim

 

[Mike Berger]

Unless it's a purely digital circuit (and possibly even
then) the different voltage level will definitely affect
its operation. Find the proper chip.

 

[[email protected]]

I have here 7805 regulator ready for use. I just dont understand if a
12 volt circuit design can be operated on 5 volts.

I'm very sorry, I was quite careless. Like someones already mentioned,
it won't work (and actually the chip will burn) if the signal levels
are too high, even though u used proper dropping at the Vcc. You may
never use higher signal level than specificated...

 

[John Robertson]

I'm very sorry, I was quite careless. Like someones already mentioned,
it won't work (and actually the chip will burn) if the signal levels
are too high, even though u used proper dropping at the Vcc. You may
never use higher signal level than specificated...

Well, actually you can interface 12V CMOS to 5V TTL if you use current
limiting resistors between the two familys. For example you can have a
12V high/low feeding into a TTL input if you put a 1.2K resistor in
series so the input protection diodes will not be blown, you can output
TTL to 12V by using open collector buffers - these (7416s for example)
can handle up to 15V with proper design.

Back in the early days MOS (17V) circuits would be directly interfaced
to TTL by some clever power supply design - split the 17 supply to
+5/-12 with the TTL running on the +5 section, then use resistors to
interface the two families. Look for Gottlieb System 1 MPU schematics
for some ideas.

Don Lancaster's CMOS Cookbook covers this TTL/CMOS as well, and I think
the TTL Cookbook mentions interfacing as well.

John :-#)#
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