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garyStofer / AIR_TFT_12ADC

12x ADC for EGT and CHT on a TFT display using an ATMEGA 328P controller
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question about thermocouple inputs #1

Open rocketbob opened 6 years ago

rocketbob commented 6 years ago

Are your K-type thermocouples connected directly to the LTC2495 or is there any signal conditioning or isolation in-between?

garyStofer commented 6 years ago

Yes the gain in the LTC is set so that the TC probes go directly on it’s inputs.

My application is on an aircraft motor and I found that all but one of my probes had a short to chassis at the tip, inherently in the way they are made. This together with current from the alternator flowing through the chassis caused ground loops in the returns of the various probes, so I decided to use differential input pairs on the LTC, therefore reducing the number of probes down to 8 per device. Using weak pull ups on the +inputs and weak pull downs on the – inputs I bias the input common mode to be in the middle of the devices input range. This also serves as a indication for an open TC because the signal rails in that case. Off the top of my head I think I used 330 or 470K resistors. Also, this requires that the power supply for the device is ground free, a DC to DC converter followed by a linear regulator is needed ( or a separate battery).

Maybe your application is not hampered by the above application issue and you can use the single input/ shared common mode the deice offers.

Cheers

Gary

From: rocketbob Sent: Monday, February 12, 2018 6:37 AM To: garyStofer/AIR_TFT_12ADC Cc: Subscribed Subject: [garyStofer/AIR_TFT_12ADC] question about thermocouple inputs (#1)

Are your K-type thermocouples connected directly to the LTC2495 or is there any signal conditioning or isolation in-between?

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rocketbob commented 6 years ago

Thanks for the info Gary.

My application is exactly the same thing, EGT/CHT's on a Lycoming (RV-6). Probes are grounded K-type. I was previously using max6675's and as I recall those devices use a similar pull-up/down scheme.

Thanks, Bob

garyStofer commented 6 years ago

Yes, -- I have an RV8 with a Franklin 220 & CS prop , but this went into my Stinson with the same engine.

if you get my PCB fro the board from OSH note that I have not completely modified it for the pull resistors yet, There where 2 cuts and jumpers needed and wider screw terminals with the wider spacing to skip over the GND pins.

From: rocketbob Sent: Monday, February 12, 2018 9:49 AM To: garyStofer/AIR_TFT_12ADC Cc: Gary Stofer ; Comment Subject: Re: [garyStofer/AIR_TFT_12ADC] question about thermocouple inputs (#1)

Thanks for the info Gary.

My application is exactly the same thing, EGT/CHT's on a Lycoming (RV-6). Probes are grounded K-type. I was previously using max6675's and as I recall those devices use a similar pull-up/down scheme.

Thanks, Bob

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rocketbob commented 6 years ago

Love the Franklin 220. I used to maintain a Stinson with one. Have a neighbor that has a 108 with the 165. I'm also building a F1 with a 540. A friend of mine who passed away a few years ago was the originator of the Super 8, and he used to let me fly his -8 with the 540. Another friend of mine inherited the engine mount jig. You're going to miss that 220 in the -8!

Is the PCB available on Oshpark? If so I don't see it.

garyStofer commented 6 years ago

Yes it’s on OSH – Search for “16xPGA_ADC”.

Their perma links and http embedded links don’t work anymore otherwise I would send you the link. I take it you found the schematic files on Gitub..

I have one unpopulated board from the intimal order. I can send it to you for $9 plus postage if you want to. There are two resistors with cuts and jumpers on the backside. Soldering the chip requires a microscope or equivalent microscopic eyesight and experience....

Let me know.

Cheers
Gary

From: rocketbob Sent: Monday, February 12, 2018 12:38 PM To: garyStofer/AIR_TFT_12ADC Cc: Gary Stofer ; Comment Subject: Re: [garyStofer/AIR_TFT_12ADC] question about thermocouple inputs (#1)

Love the Franklin 220. I used to maintain a Stinson with one. Have a neighbor that has a 108 with the 165. I'm also building a F1 with a 540. A friend of mine who passed away a few years ago was the originator of the Super 8, and he used to let me fly his -8 with the 540. Another friend of mine inherited the engine mount jig. You're going to miss that 220 in the -8!

Is the PCB available on Oshpark? If so I don't see it.

— You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

rocketbob commented 6 years ago

Yes I definitely will take the board. Just shoot me your email and I will paypal you. I just got some sample LTC2495's yesterday and was contemplating how to prototype. I have a smt soldering microscope, hot air, etc.

Thanks, Bob

On Tue, Feb 13, 2018 at 1:22 AM, Gary Stofer notifications@github.com wrote:

Yes it’s on OSH – Search for “16xPGA_ADC”.

Their perma links and http embedded links don’t work anymore otherwise I would send you the link. I take it you found the schematic files on Gitub..

I have one unpopulated board from the intimal order. I can send it to you for $9 plus postage if you want to. There are two resistors with cuts and jumpers on the backside. Soldering the chip requires a microscope or equivalent microscopic eyesight and experience....

Let me know.

Cheers Gary

From: rocketbob Sent: Monday, February 12, 2018 12:38 PM To: garyStofer/AIR_TFT_12ADC Cc: Gary Stofer ; Comment Subject: Re: [garyStofer/AIR_TFT_12ADC] question about thermocouple inputs (#1)

Love the Franklin 220. I used to maintain a Stinson with one. Have a neighbor that has a 108 with the 165. I'm also building a F1 with a 540. A friend of mine who passed away a few years ago was the originator of the Super 8, and he used to let me fly his -8 with the 540. Another friend of mine inherited the engine mount jig. You're going to miss that 220 in the -8!

Is the PCB available on Oshpark? If so I don't see it.

— You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

— You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub https://github.com/garyStofer/AIR_TFT_12ADC/issues/1#issuecomment-365162943, or mute the thread https://github.com/notifications/unsubscribe-auth/AAWWcp1EXfoiLSQSxt0wtMCSeACoHq_eks5tUSoWgaJpZM4SCQ5T .

garyStofer commented 6 years ago

Excellent -- PP me at garystofer@hotmail.com -

I figure a flat pack in the US comes to about $4, so send about $13 and your address so I can get it out today ( I’m out of town for the rest of the week). If you are interested in the code for the project I can check it in to Github. I think there is something there already, but I probably have some revised version sitting on the dev machine still. It’s using an ATMEL 328P aka Arduino and I’m using a controller board I made for a 2 1/4”round instrument hole with a one of those 240x180 graphic LCDs do display bars. It’s just big enough to display 6 bars at a time and conveniently read it without having to take the magnifying glass. The main PCB is also on OSH under Air_LCDuino, has a rotary knob and the same footprint as the ADC. I don’t have any extras of those however. Note that I didn’t use the SD card slot on the ADC board but instead the bigger one that’s on the LCD board.

I mounted the ADC board right on the firewall ( cold side) and then only have to run a 4 wire cable to the instrument head. Slowed I2C speed to 20Khz ( I think) .

Gary

Cc: Gary Stofer ; Comment Subject: Re: [garyStofer/AIR_TFT_12ADC] question about thermocouple inputs (#1)

Yes I definitely will take the board. Just shoot me your email and I will paypal you. I just got some sample LTC2495's yesterday and was contemplating how to prototype. I have a smt soldering microscope, hot air, etc.

Thanks, Bob

On Tue, Feb 13, 2018 at 1:22 AM, Gary Stofer notifications@github.com wrote:

Yes it’s on OSH – Search for “16xPGA_ADC”.

Their perma links and http embedded links don’t work anymore otherwise I would send you the link. I take it you found the schematic files on Gitub..

I have one unpopulated board from the intimal order. I can send it to you for $9 plus postage if you want to. There are two resistors with cuts and jumpers on the backside. Soldering the chip requires a microscope or equivalent microscopic eyesight and experience....

Let me know.

Cheers Gary

From: rocketbob Sent: Monday, February 12, 2018 12:38 PM To: garyStofer/AIR_TFT_12ADC Cc: Gary Stofer ; Comment Subject: Re: [garyStofer/AIR_TFT_12ADC] question about thermocouple inputs (#1)

Love the Franklin 220. I used to maintain a Stinson with one. Have a neighbor that has a 108 with the 165. I'm also building a F1 with a 540. A friend of mine who passed away a few years ago was the originator of the Super 8, and he used to let me fly his -8 with the 540. Another friend of mine inherited the engine mount jig. You're going to miss that 220 in the -8!

Is the PCB available on Oshpark? If so I don't see it.

— You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

— You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub https://github.com/garyStofer/AIR_TFT_12ADC/issues/1#issuecomment-365162943, or mute the thread https://github.com/notifications/unsubscribe-auth/AAWWcp1EXfoiLSQSxt0wtMCSeACoHq_eks5tUSoWgaJpZM4SCQ5T .

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garyStofer commented 6 years ago

here is the permalink for the “mother” board https://oshpark.com/shared_projects/kT6TDwLU

From: rocketbob Sent: Tuesday, February 13, 2018 5:25 AM To: garyStofer/AIR_TFT_12ADC Cc: Gary Stofer ; Comment Subject: Re: [garyStofer/AIR_TFT_12ADC] question about thermocouple inputs (#1)

Yes I definitely will take the board. Just shoot me your email and I will paypal you. I just got some sample LTC2495's yesterday and was contemplating how to prototype. I have a smt soldering microscope, hot air, etc.

Thanks, Bob

On Tue, Feb 13, 2018 at 1:22 AM, Gary Stofer notifications@github.com wrote:

Yes it’s on OSH – Search for “16xPGA_ADC”.

Their perma links and http embedded links don’t work anymore otherwise I would send you the link. I take it you found the schematic files on Gitub..

I have one unpopulated board from the intimal order. I can send it to you for $9 plus postage if you want to. There are two resistors with cuts and jumpers on the backside. Soldering the chip requires a microscope or equivalent microscopic eyesight and experience....

Let me know.

Cheers Gary

From: rocketbob Sent: Monday, February 12, 2018 12:38 PM To: garyStofer/AIR_TFT_12ADC Cc: Gary Stofer ; Comment Subject: Re: [garyStofer/AIR_TFT_12ADC] question about thermocouple inputs (#1)

Love the Franklin 220. I used to maintain a Stinson with one. Have a neighbor that has a 108 with the 165. I'm also building a F1 with a 540. A friend of mine who passed away a few years ago was the originator of the Super 8, and he used to let me fly his -8 with the 540. Another friend of mine inherited the engine mount jig. You're going to miss that 220 in the -8!

Is the PCB available on Oshpark? If so I don't see it.

— You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

— You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub https://github.com/garyStofer/AIR_TFT_12ADC/issues/1#issuecomment-365162943, or mute the thread https://github.com/notifications/unsubscribe-auth/AAWWcp1EXfoiLSQSxt0wtMCSeACoHq_eks5tUSoWgaJpZM4SCQ5T .

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garyStofer commented 6 years ago

got the money, will go out tomorrow via USPS –

Keep me posted of your progress .

Thanks

Gary

From: rocketbob Sent: Tuesday, February 13, 2018 5:25 AM To: garyStofer/AIR_TFT_12ADC Cc: Gary Stofer ; Comment Subject: Re: [garyStofer/AIR_TFT_12ADC] question about thermocouple inputs (#1)

Yes I definitely will take the board. Just shoot me your email and I will paypal you. I just got some sample LTC2495's yesterday and was contemplating how to prototype. I have a smt soldering microscope, hot air, etc.

Thanks, Bob

On Tue, Feb 13, 2018 at 1:22 AM, Gary Stofer notifications@github.com wrote:

Yes it’s on OSH – Search for “16xPGA_ADC”.

Their perma links and http embedded links don’t work anymore otherwise I would send you the link. I take it you found the schematic files on Gitub..

I have one unpopulated board from the intimal order. I can send it to you for $9 plus postage if you want to. There are two resistors with cuts and jumpers on the backside. Soldering the chip requires a microscope or equivalent microscopic eyesight and experience....

Let me know.

Cheers Gary

From: rocketbob Sent: Monday, February 12, 2018 12:38 PM To: garyStofer/AIR_TFT_12ADC Cc: Gary Stofer ; Comment Subject: Re: [garyStofer/AIR_TFT_12ADC] question about thermocouple inputs (#1)

Love the Franklin 220. I used to maintain a Stinson with one. Have a neighbor that has a 108 with the 165. I'm also building a F1 with a 540. A friend of mine who passed away a few years ago was the originator of the Super 8, and he used to let me fly his -8 with the 540. Another friend of mine inherited the engine mount jig. You're going to miss that 220 in the -8!

Is the PCB available on Oshpark? If so I don't see it.

— You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

— You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub https://github.com/garyStofer/AIR_TFT_12ADC/issues/1#issuecomment-365162943, or mute the thread https://github.com/notifications/unsubscribe-auth/AAWWcp1EXfoiLSQSxt0wtMCSeACoHq_eks5tUSoWgaJpZM4SCQ5T .

— You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.