12volt check

[Big House]

Hello

I need a simple circuit (DC 0-15 volts) that does:

if Vin<=12 then Vout=0 (or anything less than 5 volts is fine)
if Vin>12 then Vout=Vin

would you post the circuit or let me know where I can find one or how I
can do it?

Thanks

 

[Ken Taylor]

Hello

I need a simple circuit (DC 0-15 volts) that does:

if Vin<=12 then Vout=0 (or anything less than 5 volts is fine)
if Vin>12 then Vout=Vin

would you post the circuit or let me know where I can find one or how I
can do it?

Thanks

Resistor and 12V zener to the base of a transistor driving a relay.

Cheers.

Ken

 

[john]

Hi,

Check out maxim's voltage monitoring chips at their websites.

Bye

 

[Jim Thompson]

Hello

I need a simple circuit (DC 0-15 volts) that does:

if Vin<=12 then Vout=0 (or anything less than 5 volts is fine)
if Vin>12 then Vout=Vin

would you post the circuit or let me know where I can find one or how I
can do it?

Thanks

http://www.analog-innovations.com/SED/LevelDetectAndFollow.pdf

Use LM324 for the OpAmp, making sure that its VDD is at least 2V
higher than the largest desired input.

...Jim Thompson

 

[Jim Thompson]

http://www.analog-innovations.com/SED/LevelDetectAndFollow.pdf

Use LM324 for the OpAmp, making sure that its VDD is at least 2V
higher than the largest desired input.

...Jim Thompson

It can be done with only two OpAmps, but I'll "leave that as an
exercise for the student" ;-)

...Jim Thompson

 

[Fred Bloggs]

I need a simple circuit (DC 0-15 volts) that does:

if Vin<=12 then Vout=0 (or anything less than 5 volts is fine)
if Vin>12 then Vout=Vin

would you post the circuit or let me know where I can find one or how I
can do it?

Something like this provides a sharp turn-on/off:
View in a fixed-width font such as Courier.

 

[Big House]

Hello

v ery impressive, thanks! However I do not have a +12volt source, just
Vin...

is there a way to do it?

Thanks

 

[Jim Thompson]

Hello

v ery impressive, thanks! However I do not have a +12volt source, just
Vin...

is there a way to do it?

Thanks

Probably. The relay idea will do that. Also Bloggs has a submission,
which I'm sure works ;-)

...Jim Thompson

 

[Fred Bloggs]

Hello

I need a simple circuit (DC 0-15 volts) that does:

if Vin<=12 then Vout=0 (or anything less than 5 volts is fine)
if Vin>12 then Vout=Vin

would you post the circuit or let me know where I can find one or how I
can do it?

Thanks

This is a bit more linear- good snap action- adjust pot for
approximately midway and confirm switchpoint with VOM. It draws about
35mA at 15V, and if you don't like that then you need a bandgap
reference and some other parts:
View in a fixed-width font such as Courier.

 

[martin griffith]

Probably. The relay idea will do that. Also Bloggs has a submission,
which I'm sure works ;-)

...Jim Thompson

This Bloggs bloke is OK aint he


martin

 

[Jim Thompson]

This Bloggs bloke is OK aint he


martin

Yep. Keeps me scrambling ;-)

See...

http://www.analog-innovations.com/SED/LevelDetectAndFollow-TL431.pdf

...Jim Thompson

 

[Fred Bloggs]

Yep. Keeps me scrambling ;-)

See...

http://www.analog-innovations.com/SED/LevelDetectAndFollow-TL431.pdf

...Jim Thompson

Well- if a relay is required then he needs to current limit at 15V, like so:
View in a fixed-width font such as Courier.

 

[Fred Bloggs]

Hello

I need a simple circuit (DC 0-15 volts) that does:

if Vin<=12 then Vout=0 (or anything less than 5 volts is fine)
if Vin>12 then Vout=Vin

would you post the circuit or let me know where I can find one or how I
can do it?

Thanks

You can control indefinitely large loads with a relay- but some of them
are fussy about 25% overdrive so you have to current limit.
View in a fixed-width font such as Courier.

 

[Fred Bloggs]

Hello

I need a simple circuit (DC 0-15 volts) that does:

if Vin<=12 then Vout=0 (or anything less than 5 volts is fine)
if Vin>12 then Vout=Vin

would you post the circuit or let me know where I can find one or how I
can do it?

Thanks

And you don't need the stop diode for the relay circuit:
View in a fixed-width font such as Courier.

 

[eehinjor]

use a thansistor to realize a compartor is OK.

 

[[email protected]]

Big House wrote:

You can control indefinitely large loads with a relay- but some of them
are fussy about 25% overdrive so you have to current limit.

But theyre happy with 20% underdrive, so can just use a series resistor
to translate 12-15v to 9.6-12v.


NT

 

[John Fields]

Hello

I need a simple circuit (DC 0-15 volts) that does:

if Vin<=12 then Vout=0 (or anything less than 5 volts is fine)
if Vin>12 then Vout=Vin

would you post the circuit or let me know where I can find one or how I
can do it?

---
I have a couple of circuits I can post for you, but first:

1. How much current can your 0-15V input source?

2. How much current will your load need when Vin >= 12V?

 

[ehsjr]

http://www.analog-innovations.com/SED/LevelDetectAndFollow.pdf

Use LM324 for the OpAmp, making sure that its VDD is at least 2V
higher than the largest desired input.

...Jim Thompson

Hmmm... what am I doing wrong? I breadboarded it, and I get
about 1.3 Vout when under threshold with threshold anywhere
from 5 to 12 volts and a 17 volt supply. (Didn't try above
12 or below 5). It switches nicely from low to Vin when
you sweep over the threshold. I'm using a 5K pot to pin 2 of
U1 for the threshold voltage, and another 5K pot to pin 3
for the sweep voltage.

It's a nice circuit. Like they say in the cereal commercial:
"Mikey likes it!"

Ed

 

[Jasen Betts]

Hello

I need a simple circuit (DC 0-15 volts) that does:

if Vin<=12 then Vout=0 (or anything less than 5 volts is fine)
if Vin>12 then Vout=Vin

_-
1n ----+-----+------+----o~. o------------> out
| | | .
| | | ______
| \6K8 |___| _-~|_____.
/ / | |_-~ | |
10K \ \ | ~~~~~~ |
/ / +-----|<---------|
\ | | |
| | +|\| |
+-----(----| \ | /
| | | \ |/
| | |741>----[2K2]--|
5.1V | | | / |\
__L_| +----| / | \|
|/^\ | |/| ~\
| / | |
| \ | |
| / | |
| \ 5k1 | |
| | | |
| | | |
------+-----+------+----------------+-

for the relay and transistor it depends on the load you want to switch.

if high precision and temperature stability is needed a precision voltage
source could be used instead of the zener diode

 

[Jim Thompson]

Hmmm... what am I doing wrong? I breadboarded it, and I get
about 1.3 Vout when under threshold with threshold anywhere
from 5 to 12 volts and a 17 volt supply. (Didn't try above
12 or below 5). It switches nicely from low to Vin when
you sweep over the threshold. I'm using a 5K pot to pin 2 of
U1 for the threshold voltage, and another 5K pot to pin 3
for the sweep voltage.

It's a nice circuit. Like they say in the cereal commercial:
"Mikey likes it!"

Ed

You're not doing anything wrong, it seems to be working as the OP
requested ;-)

It can be done with only two OpAmps. Has anyone figured out how yet?

...Jim Thompson