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Lm335z

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tytower

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I am looking for some data sheets or diagrams to tell me how to set my comparitor LM393 to enable the use of this sensor down to the 0 degrees C to -10 C. Im using the Jaycar Tempmaster MK2 kit which is based on the Silicon chip article in Feb 2009

Anybody have any sites ?
Thanks
 

ericgibbs

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I am looking for some data sheets or diagrams to tell me how to set my comparitor LM393 to enable the use of this sensor down to the 0 degrees C to -10 C. Im using the Jaycar Tempmaster MK2 kit which is based on the Silicon chip article in Feb 2009

Anybody have any sites ?
Thanks
hi,
The basic range of the LM335 is -40C thru +100C at 10mV/C.
So at -10C you will get 30 * 0.01= 0.3VΔ and at 0C 0.4VΔ.
NOTE: the offset is from absolute zero -273C, these values are relative from -40C.

Are you asking for a LM393 circuit that switches at -10C and 0C, ie: a window comparator.??

Do you follow OK.?
 
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tytower

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I need to be able to vary the cut in point of a temperature controller ,the LM335Z
The voltage drop on this sensor is 2.67v at -6C linearly to 2.75v at 2C.
Thats 0.01v per 1 degree C.

The kit is made with comparitor resistor values to give a range of 2 C to 19 C for cooling .
I would like to adjust that to say -10C to +6C
 

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tytower

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hi,
The basic range of the LM335 is -40C thru +100C at 10mV/C.
So at -10C you will get 30 * 0.01= 0.3VΔ and at 0C 0.4VΔ.
NOTE: the offset is from absolute zero -273C, these values are relative from -40C.

Are you asking for a LM393 circuit that switches at -10C and 0C, ie: a window comparator.??

Do you follow OK.?
Err I don't think.. you got this right, it reads 2.73v at 0C and 2.93v at say 20C so at -10 C it would be 2.63v .I don't know what you mean by the Delta sign .....0.3v change? 0.4v change?
 

ericgibbs

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Err I don't think.. you got this right, it reads 2.73v at 0C and 2.93v at say 20C so at -10 C it would be 2.63v .I don't know what you mean by the Delta sign .....0.3v change? 0.4v change?
hi,
Look at this LTS sim of the modified circuit. [ignore the relay part]

The delta was using the -40C for the reference, I know it 0mV at 273K.:)

This gives 2.63V [-10C] and 2.79 [+6c]

Hope you follow it OK.
 

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ericgibbs

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hi,
If you need to have the comp to switch in the opposite sense, use this circuit.
Changes are: swop the LM393 inputs over and reduce the hysteresis resistor [R7] to approx 97K.

I would use a 82K resistor and a 50K pot in series, this will enable adjustment of the switching limits.

On the first circuit a 430K and 200Kpot would allow adjustment.
 

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tytower

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Eric is this supposed to be the original circuit or is it something else ?
In both the circuits you have the comparitor + feed coming off after the 3.3k resistor. This is not the case ,it comes off before

What is the significance of the time graph?
I can see the voltages at which the comparitor switches off and on but what do the Ms mean.

I am trying to make sense of this -I know its probably me ! I have downloaded LTSpice IV which is freeware and am trying to make it work.

Can I copy this .gif file somehow or can you post the .asc file so I may import it ?
 
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ericgibbs

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Eric is this supposed to be the original circuit or is it something else ?
In both the circuits you have the comparitor + feed coming off after the 3.3k resistor. This is not the case ,it comes off before

What is the significance of the time graph?
I can see the voltages at which the comparitor switches off and on but what do the Ms mean.

I am trying to make sense of this -I know its probably me ! I have downloaded LTSpice IV which is freeware and am trying to make it work.

Can I copy this .gif file somehow or can you post the .asc file so I may import it ?
hi,
See attached the two *.asc files, you will need to get the LM393A and Relay models from the LTSpice Yahoo site.

I can easily change the take off point to the other side of the 3K3 if you prefer.?
I'll change it for you and repost.:)

The graphs show in voltage/temperature [LM355] the ON/OFF tempr of the circuits, in both senses of the LM393.
The mS is just the time base for the LTS sim run.
 

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tytower

Banned
Thanks -Working on it
 

tytower

Banned
Well Eric I got some files from yahoo although the DLED_RD and the 1N4006 I could not find and the simulation complained that it needed them so on my circuit I changed them to something it had .

See attached

But now from here how do I get it to show me when it switches on and off?
I can measure voltages etc and they show on the graph but can I get a meter circuit so I can attach a meter at various points and watch the voltage change as I change values?
 

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ericgibbs

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But now from here how do I get it to show me when it switches on and off?
I can measure voltages etc and they show on the graph but can I get a meter circuit so I can attach a meter at various points and watch the voltage change as I change values?
hi.
Measuring voltages:

Run the simulation.

Select V1 and comp for plotting, you should get the plots I have posted.
Place the cross hairs cursor close to where the V1 and comp plot lines cross.
Press and hold down the left mouse key, use the dotted box to enclose the intersection of the plot lines and then release the mouse button.
[do this for the left hand crossing point]
The plot window will be magnified.

Right mouse click the V[n002] label located just above the graph, this will display the 'Expression Editor' window.
Click the 'Attached Cursor' drop down box [ initially shows 'none']
Left click the 1st option, then OK.

This will display a small window, showing the values at the '1st' cursor location.
If you move the cross hair cursor over the plot a large '1' will appear when you are over the '1st' curosr.
Press and hold down the left mouse button and 'drag' the '1st' cursor over the intersection of the two plot lines.
The display window will show the precise values at the 1st cursor location.

If you just want to check without doing the above procedure, then placing the cross hair cursor at the plot line cross over and look at the bottom left of the LTSpice window you will see the cross hair coodinates displayed.

Hope you follow that.:)

BTW: I cannot download your asc file.???

EDIT:
after a couple of tries, got the download.
 
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tytower

Banned
Geez , That program LTSpice 1V is a great find -Thanks
 
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