The output of the LM35 goes to the Inhi pin, and the ground goes to the Inlo pin.

 

Yes this is how I had it connected and it wasn't working, Playing with the Potentiometer didn't change output in any way at all as well.

 

There seems to be some mistakes in the ICL7117 circuit in the data sheet.
ICL7117 is for common Anode LED display, not multiplexed.
Pin 26 should be connected to -5V.
The bottom end of 10k preset should goto Pin 32, and should not be connected to Pin 26 or -5V.
Adjust the 10k preset, so that the voltage between Pin 32 and Pin 36 is 100mV. This will make it into a 200mV full scale meter (199.9 will be the maximum). Actually, only 1999 will be visible, and you need to turn the required decimal point!

Most importantly, the ground of this ICL7117 circuit should not be connected to the ground of LM35 circuit. InLo is connected to common and is at about 2.8V down from +5V. This is normally not a problem as ICL7117 meters are powered with battery, and normally uses a charge pump -V generator.
BTW, If you had already connected ICL7117 Gnd and external circuit Gnd (LM35), then common would have been shorted to ICL7117 Gnd, and I am not sure that the IC will survive this, more likely I am afraid it will not. Common is a reference voltage.

Good Luck!

 

Hi RamaD.

Firstly; Thank you for responding. This is the first helpful post I've gotten with regards to the circuit of the LM35 to ICL7117.

Now; I'm aware about the muliplexed display issue and I am using CA 7 segment displays.

Most importantly, the ground of this ICL7117 circuit should not be connected to the ground of LM35 circuit. InLo is connected to common and is at about 2.8V down from +5V. This is normally not a problem as ICL7117 meters are powered with battery, and normally uses a charge pump -V generator.
BTW, If you had already connected ICL7117 Gnd and external circuit Gnd (LM35), then common would have been shorted to ICL7117 Gnd, and I am not sure that the IC will survive this, more likely I am afraid it will not. Common is a reference voltage.

So what ground connection do i use for the ground pin[21] on the ICL7117?

Also how would I know if the chip isn't working?
With the current setup (before adding the changes you've suggested) all outputs of the ICl7117 were at a high (5V).

 

Ground of ICL7117 power supplies of +5V and -5V, should be connected to Pin 21.
LM35 ground is to be connected to InLo (also connected to common).
See if you can adjust the voltage between Pin 36 & Pin 32 (RefHi and common) to 100mV, and also whether the voltage is steady. Also check the voltage on common with respect to +5V. All outputs Hi at 5V, means that the display would be blank, but then the connections were not right, so hopefully nothing had happened.

My guess is you might be able to connect the grounds together, if common is not connected to InLo. But then nothing is said about this in the datasheet.
It is difficult to ascertain whether no damage happened to the chip.

 

Hi.

Have made your suggested changes.
Circuit and display works 100%.

Thanks very much for your help

 

How do I increase the conversion rate of the ICL7117?
(How do i make it convert values faster? As if I increase or decrease the temperature, the voltage output of the LM35 changes way faster than the ADC displays it through 7 segments)

 

There is nothing specified in the data sheet. It says it is a dual slope, which by integration averages out noise, over a period. Generally kept in multiples of the period of line frequency, as that is normally likely to be the dominant noise. Increasing sampling rate, reduces this ability.
You need to change the oscillator components, RC, the limits of which are not known.
Similiarly, the integrating components also need to be changed so that there would be better utilisation of the voltage swing available, or else the accuracy could be affected.
Try reducing the Cosc.
BTW, did you try disconnecting common from InLo, and connect InLo to both the 7117 Ground and input LM35 grounds?

 

Hi!

Unfortunately whilst integrating the temperature display circuit with another, something had gone wrong and I'm back to where i started!

The ADC is outputting a high at all outputs. After hours of not being able to solve the issue I disconnected the ADC and began connecting it again from the start. I've found another datasheet online from:
http://www.komponenten.es.aau.dk/fileadmin/komponenten/Data_Sheet/ADC_DAC/ICL7116_ICL7117.pdf
The circuit diagram is as follows:
where the dotted line connection between 32 and 30 IS made. The connection between 21 and 30 IS NOT made.

On this datasheet I've also found a way to test the ADC to see if it's functional (If pin 37 is sent a high all segments on display light up). I've performed this test and am confident that the chip is still operational.
However it still doesn't display anything; all outputs are at a high. If i give 37 a high to test; all segments light up. When I ground 37 all segments are off again.
I think the problem is occurring as I have no separate external digital and analog Grounds.
This is because the LM35 only outputs a high anologue signal which means i only have IN HI to the output of LM35 and no connection to IN LO (except what's represented above).

 

Hi!

Unfortunately whilst integrating the temperature display circuit with another, something had gone wrong and I'm back to where i started!

The ADC is outputting a high at all outputs. After hours of not being able to solve the issue I disconnected the ADC and began connecting it again from the start. I've found another datasheet online from:
http://www.komponenten.es.aau.dk/fileadmin/komponenten/Data_Sheet/ADC_DAC/ICL7116_ICL7117.pdf
The circuit diagram is as follows:
where the dotted line connection between 32 and 30 IS made. The connection between 21 and 30 IS NOT made.
View attachment 85591
On this datasheet I've also found a way to test the ADC to see if it's functional (If pin 37 is sent a high all segments on display light up). I've performed this test and am confident that the chip is still operational.
However it still doesn't display anything; all outputs are at a high. If i give 37 a high to test; all segments light up. When I ground 37 all segments are off again.
I think the problem is occurring as I have no separate external digital and analog Grounds.
This is because the LM35 only outputs a high anologue signal which means i only have IN HI to the output of LM35 and no connection to IN LO (except what's represented above).

LM35 has three legs. Leg 1 Power, Leg 2 Analog Output, Leg 3 Ground. I think you are on the right track. You need to connect Leg 2 of LM35 to IN HI of the ADC, connect Leg 3 of LM35 to IN LO of ADC, connect IN LO to Ground (like it is shown with the doted line) because I think LM35 is the single ended input.

 

Hi,

I applied these changes, i.e:
IN LO to GND as well as to leg 3 on LM35.

The display showed; '66' (I'm only usint 2 seven seg. displays; units and tens). I tried to re-calibrate by adjusting the potentiometer, nothing changed.

I switched the power off for a few seconds and back on again, displays are blank once again

 

That is a decent datasheet with all information. Maxim is a second source for this (as per their datasheet), and probably did not bother about the datasheet.

Making Pin 37 High tests all the display drivers only! It does not test the ADC.
Connecting Pin 32 to Gnd does not blow the chip as given in the data sheet. I was wrong in suspecting this could happen, because of the voltage on this pin. However, when Pin 32 connected to ground, will not allow the use of internal reference, and would require an external reference.

BTW, did you try disconnecting common from InLo, and connect InLo to both the 7117 Ground and input LM35 grounds?

This is what I had mentioned, which would keep all the grounds together and keep Common, Pin 32, not connected to Ground. This allows internal reference to be used.