Very Small Panel Meters

Stephane · 5th November 2007, 18:33

The DPM comes from a flooded PpO2 controler ...

I guess the IC driver has some dead outputs. The LCD itself responds to static electricity, contacts have been cleaned but it did not salvage the thing.

teomannaskali · 6th November 2007, 08:38

That is sad.

So did it have an op amp?

Teoman

Stephane · 6th November 2007, 08:44

Yes, it has an opamp. It was in a rEvodream beta version.
It's the only part that sufferd in the flood, I was diving in fresh water.

teomannaskali · 6th November 2007, 17:02

Hi Stéphane.

Could you do the following for me. Could you short the 3k resistor attached to the pot. And then set the 1.5k pot to 1.38 (Or attach an O2 cell and calibrate using the pot)

PS you still need to put a 10k resistor between the poles of the cell.

Do you have any problems with this?

I just want feedback on how hard it will be to calibrate. If the pot will bee too sensitive. And of course you indeed can get the 209 number to appear on the display.

Then at a later phase we can change the 100k with 203 k. This will give the same result except that the pot will have shorter range but be more sensitive.

Right now I am looking for batteries that I will use. According to its characteristics I will determine the exact resistance values.

Thank you very much. I am waiting for you answer.

Teoman

teomannaskali · 6th November 2007, 18:50

Just a note to myself and others who may be interested in figuring out the resistance values. The parameters are:

You want the display to read 209 when 7 - 14 mv as input Assuming you are using teledyne sensors type R22D

For me: My battery will have a voltage of 3.6 V (Lithium ion) Which is actually: 4.23V when full and 2.7V when empty.

Teoman

teomannaskali · 6th November 2007, 20:19

Ok with the lithium ion battery voltage from 4.23 to 2.7 and the cell varying from 7 to 14 mV

the gain varies about 3x. Hat is a very large number for the little trimpot on the back of the lascar.... I wonder if it will be precise enough...

Teoman

teomannaskali · 12th November 2007, 16:47

Ok.

Does anyone know how to make the lascar battery sign work? What must one do? I suppose It will give a warning sign when it approaches the lower limit for display. But how can I modify it in such a sense as to make it not display the sign when it is time to recharge a lithium ion cell.

Teoman

Edvin M · 1st December 2007, 17:50

Why would you like to open it up? You dont have to modify the inside in any kind of way to make it work. I have one which I have attached some resistors, opm-meter and a battery to and I havent opend it up.

I shall see if I can make a understandable drawing of the circuit and up it up. The only problem with the SP400 is that it only has 3 digits, I would like to have 4 but 3 is fine at the moment.

Edvin M · 1st December 2007, 18:30

Just realized something, it does have 4 digits, dont know if I shall cheer or just hit myelsf in the head a couple of times. Apparantly it's just my circuit who is ****ing it up. I have attached a picture of it, the round thing in the middle is the OP AM, does anyone know what to do to get it working i e get it to show 0.209 instead of 00.21?

teomannaskali · 1st December 2007, 19:56

The lascar is able to show the ppo2 without the need for an external op amp. You just need to change the resistors inside.

Besides that the answer to tour question.
1. you need to change un connect the DP2 and connect DP3 to V+ to get the "." in the right place.

2. You need to change the resistor values on the op amp in order to get a 10 times higher gain.

My design specs are:
1 No external op amp
2 10 k load on cell as the data sheet indicates.

I am printing the pcb and I will make it available.

Teoman

5th November 2007, 18:33	#21 (permalink)
Stephane Stéphane Acounis Current Rebreather/s: rEvo Other Rebreather/s: rEvo Join Date: Nov 2005 Location: Nantes - France Posts: 773	Re: Very Small Panel Meters The DPM comes from a flooded PpO2 controler ... I guess the IC driver has some dead outputs. The LCD itself responds to static electricity, contacts have been cleaned but it did not salvage the thing. __________________ Stéphane
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6th November 2007, 08:38	#22 (permalink)
teomannaskali Custom Title Allowed! Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Feb 2006 Location: Istanbul TR Posts: 384	Re: Very Small Panel Meters That is sad. So did it have an op amp? Teoman
(Online)

6th November 2007, 08:44	#23 (permalink)
Stephane Stéphane Acounis Current Rebreather/s: rEvo Other Rebreather/s: rEvo Join Date: Nov 2005 Location: Nantes - France Posts: 773	Re: Very Small Panel Meters Yes, it has an opamp. It was in a rEvodream beta version. It's the only part that sufferd in the flood, I was diving in fresh water. __________________ Stéphane
(Offline)

6th November 2007, 17:02	#24 (permalink)
teomannaskali Custom Title Allowed! Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Feb 2006 Location: Istanbul TR Posts: 384	Re: Very Small Panel Meters Hi Stéphane. Could you do the following for me. Could you short the 3k resistor attached to the pot. And then set the 1.5k pot to 1.38 (Or attach an O2 cell and calibrate using the pot) PS you still need to put a 10k resistor between the poles of the cell. Do you have any problems with this? I just want feedback on how hard it will be to calibrate. If the pot will bee too sensitive. And of course you indeed can get the 209 number to appear on the display. Then at a later phase we can change the 100k with 203 k. This will give the same result except that the pot will have shorter range but be more sensitive. Right now I am looking for batteries that I will use. According to its characteristics I will determine the exact resistance values. Thank you very much. I am waiting for you answer. Teoman Last edited by teomannaskali : 6th November 2007 at 17:10.
(Online)

6th November 2007, 18:50	#25 (permalink)
teomannaskali Custom Title Allowed! Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Feb 2006 Location: Istanbul TR Posts: 384	Re: Very Small Panel Meters Just a note to myself and others who may be interested in figuring out the resistance values. The parameters are: You want the display to read 209 when 7 - 14 mv as input Assuming you are using teledyne sensors type R22D For me: My battery will have a voltage of 3.6 V (Lithium ion) Which is actually: 4.23V when full and 2.7V when empty. Teoman
(Online)

6th November 2007, 20:19	#26 (permalink)
teomannaskali Custom Title Allowed! Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Feb 2006 Location: Istanbul TR Posts: 384	Re: Very Small Panel Meters Ok with the lithium ion battery voltage from 4.23 to 2.7 and the cell varying from 7 to 14 mV the gain varies about 3x. Hat is a very large number for the little trimpot on the back of the lascar.... I wonder if it will be precise enough... Teoman
(Online)

12th November 2007, 16:47	#27 (permalink)
teomannaskali Custom Title Allowed! Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Feb 2006 Location: Istanbul TR Posts: 384	Re: Very Small Panel Meters Ok. Does anyone know how to make the lascar battery sign work? What must one do? I suppose It will give a warning sign when it approaches the lower limit for display. But how can I modify it in such a sense as to make it not display the sign when it is time to recharge a lithium ion cell. Teoman
(Online)

1st December 2007, 17:50	#28 (permalink)
Edvin M New Member Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Aug 2007 Location: Lysekil, Sweden Posts: 97	Re: Very Small Panel Meters Why would you like to open it up? You dont have to modify the inside in any kind of way to make it work. I have one which I have attached some resistors, opm-meter and a battery to and I havent opend it up. I shall see if I can make a understandable drawing of the circuit and up it up. The only problem with the SP400 is that it only has 3 digits, I would like to have 4 but 3 is fine at the moment.
(Offline)

1st December 2007, 19:56	#30 (permalink)
teomannaskali Custom Title Allowed! Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Feb 2006 Location: Istanbul TR Posts: 384	Re: Very Small Panel Meters The lascar is able to show the ppo2 without the need for an external op amp. You just need to change the resistors inside. Besides that the answer to tour question. 1. you need to change un connect the DP2 and connect DP3 to V+ to get the "." in the right place. 2. You need to change the resistor values on the op amp in order to get a 10 times higher gain. My design specs are: 1 No external op amp 2 10 k load on cell as the data sheet indicates. I am printing the pcb and I will make it available. Teoman
(Online)

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