low-droput regulator questions

S

spencer

Guest
i am a newbie at electronics and am trying to build this:

http://www.geocities.com/CapeCanaveral/Launchpad/3632/pc_therm.htm

it isn't working. i may be installing the LM2936-z5 incorrectly. i am
working on the assumtion that the middle post is the ground. also, the
guy at the electronics store said that the lm2936cz-5 was the same as
the lm2936-5 just made by a different company. are either of these
correct?

thanks.
 
"spencer" <damnesia@gmail.com> wrote in message
news:8dd44715.0411062348.769c5d6c@posting.google.com...
i am a newbie at electronics and am trying to build this:

http://www.geocities.com/CapeCanaveral/Launchpad/3632/pc_therm.htm

it isn't working. i may be installing the LM2936-z5 incorrectly. i am
working on the assumtion that the middle post is the ground. also, the
guy at the electronics store said that the lm2936cz-5 was the same as
the lm2936-5 just made by a different company. are either of these
correct?

thanks.
Click to expand...
The TO92 version (Like a transistor) has input - gnd - output when viewed
holding the pins facing towards you and the flat on the bottom.
Download the data sheet from the National site.

--
Regards ........... Rheilly Phoull
 
"Rheilly Phoull" <Rheilly@bigpong.com> wrote in message
news:2v631gF2h2rgcU1@uni-berlin.de...
"spencer" <damnesia@gmail.com> wrote in message
news:8dd44715.0411062348.769c5d6c@posting.google.com...
i am a newbie at electronics and am trying to build this:

http://www.geocities.com/CapeCanaveral/Launchpad/3632/pc_therm.htm

it isn't working. i may be installing the LM2936-z5 incorrectly. i am
working on the assumtion that the middle post is the ground. also, the
guy at the electronics store said that the lm2936cz-5 was the same as
the lm2936-5 just made by a different company. are either of these
correct?

thanks.

The TO92 version (Like a transistor) has input - gnd - output when viewed
holding the pins facing towards you and the flat on the bottom.
Download the data sheet from the National site.

--
Regards ........... Rheilly Phoull


Reading from left to right that is !!
Click to expand...
 
spencer wrote:
i am a newbie at electronics and am trying to build this:

http://www.geocities.com/CapeCanaveral/Launchpad/3632/pc_therm.htm

it isn't working. i may be installing the LM2936-z5 incorrectly. i am
working on the assumtion that the middle post is the ground. also, the
guy at the electronics store said that the lm2936cz-5 was the same as
the lm2936-5 just made by a different company. are either of these
correct?

thanks.
Click to expand...
You might have fried the regulator. You can easily test it with a few
batteries, a resistor, and a multimeter.

4 AA cells, connected up in series, along with a 1k resistor, hooked up
as follows:

LM2936-5
.-------.
|in out|
.-----| |---.
| | gnd | |
| '-------' |
+ | | |
--- | |
- | o------------ DMM +
| | | ^
+ | | | |
--- | | |
- | \ |
| | / 1k | 5V
+ | | \ |
--- | / |
- | | |
| | | v
+ | | o------------- DMM -
--- | |
- | |
| | |
| | |
'---------o-------'

Hold the LM2936 case with the markings (flat side) towards you,
and the pins down. Then the left pin is Vout, the
middle pin is GND, and the right pin is Vin.

Use 1.5V AA batteries to test. 4 in series = 6V. The minimum input
voltage is 5.5 for the LM2936

created by Andy´s ASCII-Circuit v1.25.250804 www.tech-chat.de

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.
 
spencer wrote:
i am a newbie at electronics and am trying to build this:

http://www.geocities.com/CapeCanaveral/Launchpad/3632/pc_therm.htm

it isn't working. i may be installing the LM2936-z5 incorrectly. i am
working on the assumtion that the middle post is the ground. also, the
guy at the electronics store said that the lm2936cz-5 was the same as
the lm2936-5 just made by a different company. are either of these
correct?

thanks.
Click to expand...
The CTS-line will put out voltage before the supply voltage is generated.
This will blow the temperature sensors. They will then have a huge current
draw and the regulator cannot supply that and stays at a voltage around 1V.
The whole design shows your digital abilities, but adaequate skills in
analog seem to be missing.
--
ciao Ban
Bordighera, Italy
 
Ban wrote:
spencer wrote:

i am a newbie at electronics and am trying to build this:

http://www.geocities.com/CapeCanaveral/Launchpad/3632/pc_therm.htm

it isn't working. i may be installing the LM2936-z5 incorrectly. i am
working on the assumtion that the middle post is the ground. also, the
guy at the electronics store said that the lm2936cz-5 was the same as
the lm2936-5 just made by a different company. are either of these
correct?

thanks.


The CTS-line will put out voltage before the supply voltage is generated.
This will blow the temperature sensors. They will then have a huge current
draw and the regulator cannot supply that and stays at a voltage around 1V.
The whole design shows your digital abilities, but adaequate skills in
analog seem to be missing.
Click to expand...
CTS is an input to the PC. RTS or DTR might come up initially, but the
inputs are protected using those 4.7k resistors and 5.1V zeners. I'm not
sure how much protection that really gives, though. A diode from the SCL
and SDA lines to the 5V rail might help if this is really a problem.
That would certainly prevent the inputs from getting much higher than Vcc.

This would probably be a better parallel port project, actually,
although I think the programming would be harder. Using the parallel
port, he could dispense with the regulator altogether, since it's all 5V.

Also, I don't think the OP designed it.


--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.
 
Robert Monsen wrote:
The CTS-line will put out voltage before the supply voltage is
generated. This will blow the temperature sensors. They will then
have a huge current draw and the regulator cannot supply that and
stays at a voltage around 1V. The whole design shows your digital
abilities, but adaequate skills in analog seem to be missing.

CTS is an input to the PC. RTS or DTR might come up initially, but the
inputs are protected using those 4.7k resistors and 5.1V zeners. I'm
not sure how much protection that really gives, though. A diode from
the SCL and SDA lines to the 5V rail might help if this is really a
problem. That would certainly prevent the inputs from getting much higher
than
Vcc.
This would probably be a better parallel port project, actually,
although I think the programming would be harder. Using the parallel
port, he could dispense with the regulator altogether, since it's all
5V.
Also, I don't think the OP designed it.
Click to expand...
We do not have an RS232 protocoll here, but the designer tries to simulate a
two wire bus with SCL (system clock) and SDA (bidirectional data) the sensor
only functions if SDA receives the right address, so the SDA will always
send from the PC to poll data from the sensors. even if the line cannot go
above 6V with the 50mA output current of an RS232 driver, this is enough to
drive the sensors into a latch up when the supply voltage is not yet at +5V,
generating high supply current and eventually destroying the sensors.
I do not think this circuit will work as drawn on the website, even if the
guy claims to have won "design" prices, well maybe from Elektor. :)
The only reasonable solution would be to use a dedicated RS232 driver IC
here.
--
ciao Ban
Bordighera, Italy
 
spencer wrote:
Robert Monsen <rcsurname@comcast.net> wrote in message news:<3OVjd.588955$8_6.195217@attbi_s04>...
spencer wrote:


thanks for all the responses. i do/did have the regulator installed
correctly. at the Vin side i am getting 9V, the Vout side nothing.
this is a new regulator(it appears the old one was still good, but i
used a new one to be thorough). is 9V to much?

thanks again to everyone for their suggestions and help.


The max input voltage is 40V. Take a look at the datasheet here:

http://cache.national.com/ds/LM/LM2936.pdf

I'm not sure what to tell you. Did you test the regulator in a separate
battery powered circuit, like I indicated in another branch of this thread?

Note that if Ban is correct, there will be a short through the
temperature probe, and it'll pull the output voltage down. Thus, if you
are testing the regulator in circuit, that may be your problem.
sorry it has taken so long to reply, been really busy with work
stuffs.

i took a new regulator and tested it with a new 9V battery. to do this
i put the regulator on a breadboard, hooked the batterie's - side to
the ground on the regulator. the the + side to the Vin. i set my volt
meter to "20". at Vin it reads 9.66V at Vout it reads 7.29V. something
interesting, according to the pdf datasheet below using the flat part
of th to-92 the left pin is Vin. if i hook it up like that the voltage
reads the same at both sides(9.33 i think).

i think that i must be missing something.
Click to expand...
No, you need to look at the datasheet again. That view is from the
bottom. Thus, with the flat part facing you, and the pins down, the pins are

1 2 3
VOUT GND VIN

If you put a reverse voltage on most regulators, they will be destroyed
in short order. However, this one has 'reverse battery protection'. I am
not sure if that means you can reverse VOUT and VIN, or if it means you
can reverse VIN and GND. It actually looks like it might withstand this
from the schematic in the datasheet, so who knows?

You may also need a load on the regulator. Use a 1k from VOUT to ground.

Also, the datasheet calls for capacitors on input and output. However,
since you are driven by a battery, that doesn't seem that important. If
you have a 0.1uF cap and a 10uF cap, put the 0.1uF cap on the input, and
the 10uF cap on the output.

Other than that, I don't have any suggestions.

Good luck.

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.
 
Robert Monsen <rcsurname@comcast.net> wrote in message news:<3OVjd.588955$8_6.195217@attbi_s04>...
spencer wrote:

thanks for all the responses. i do/did have the regulator installed
correctly. at the Vin side i am getting 9V, the Vout side nothing.
this is a new regulator(it appears the old one was still good, but i
used a new one to be thorough). is 9V to much?

thanks again to everyone for their suggestions and help.

The max input voltage is 40V. Take a look at the datasheet here:

http://cache.national.com/ds/LM/LM2936.pdf

I'm not sure what to tell you. Did you test the regulator in a separate
battery powered circuit, like I indicated in another branch of this thread?

Note that if Ban is correct, there will be a short through the
temperature probe, and it'll pull the output voltage down. Thus, if you
are testing the regulator in circuit, that may be your problem.
Click to expand...


actually nevermind. i got it to work. using batteries instead of
trying to power it off the serial port. thanks for the help.
 
Robert Monsen <rcsurname@comcast.net> wrote in message news:<kQGjd.61108$HA.28724@attbi_s01>...
Ban wrote:
spencer wrote:

i am a newbie at electronics and am trying to build this:

http://www.geocities.com/CapeCanaveral/Launchpad/3632/pc_therm.htm

it isn't working. i may be installing the LM2936-z5 incorrectly. i am
working on the assumtion that the middle post is the ground. also, the
guy at the electronics store said that the lm2936cz-5 was the same as
the lm2936-5 just made by a different company. are either of these
correct?

thanks.


The CTS-line will put out voltage before the supply voltage is generated.
This will blow the temperature sensors. They will then have a huge current
draw and the regulator cannot supply that and stays at a voltage around 1V.
The whole design shows your digital abilities, but adaequate skills in
analog seem to be missing.

CTS is an input to the PC. RTS or DTR might come up initially, but the
inputs are protected using those 4.7k resistors and 5.1V zeners. I'm not
sure how much protection that really gives, though. A diode from the SCL
and SDA lines to the 5V rail might help if this is really a problem.
That would certainly prevent the inputs from getting much higher than Vcc.

This would probably be a better parallel port project, actually,
although I think the programming would be harder. Using the parallel
port, he could dispense with the regulator altogether, since it's all 5V.

Also, I don't think the OP designed it.
Click to expand...
thanks for all the responses. i do/did have the regulator installed
correctly. at the Vin side i am getting 9V, the Vout side nothing.
this is a new regulator(it appears the old one was still good, but i
used a new one to be thorough). is 9V to much?

thanks again to everyone for their suggestions and help.
 
spencer wrote:
thanks for all the responses. i do/did have the regulator installed
correctly. at the Vin side i am getting 9V, the Vout side nothing.
this is a new regulator(it appears the old one was still good, but i
used a new one to be thorough). is 9V to much?

thanks again to everyone for their suggestions and help.
Click to expand...
The max input voltage is 40V. Take a look at the datasheet here:

http://cache.national.com/ds/LM/LM2936.pdf

I'm not sure what to tell you. Did you test the regulator in a separate
battery powered circuit, like I indicated in another branch of this thread?

Note that if Ban is correct, there will be a short through the
temperature probe, and it'll pull the output voltage down. Thus, if you
are testing the regulator in circuit, that may be your problem.

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.
 
sorry it has taken so long to reply, been really busy with work
stuffs.

i took a new regulator and tested it with a new 9V battery. to do this
i put the regulator on a breadboard, hooked the batterie's - side to
the ground on the regulator. the the + side to the Vin. i set my volt
meter to "20". at Vin it reads 9.66V at Vout it reads 7.29V. something
interesting, according to the pdf datasheet below using the flat part
of th to-92 the left pin is Vin. if i hook it up like that the voltage
reads the same at both sides(9.33 i think).

i think that i must be missing something.


Robert Monsen <rcsurname@comcast.net> wrote in message news:<3OVjd.588955$8_6.195217@attbi_s04>...
spencer wrote:

thanks for all the responses. i do/did have the regulator installed
correctly. at the Vin side i am getting 9V, the Vout side nothing.
this is a new regulator(it appears the old one was still good, but i
used a new one to be thorough). is 9V to much?

thanks again to everyone for their suggestions and help.

The max input voltage is 40V. Take a look at the datasheet here:

http://cache.national.com/ds/LM/LM2936.pdf

I'm not sure what to tell you. Did you test the regulator in a separate
battery powered circuit, like I indicated in another branch of this thread?

Note that if Ban is correct, there will be a short through the
temperature probe, and it'll pull the output voltage down. Thus, if you
are testing the regulator in circuit, that may be your problem.
Click to expand...
 
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