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PaxInstruments / t400-electronics

Electronics for the Pax Instruments T400 temperature datalogger
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Change component values to reflect what is available #88

Closed charlespax closed 9 years ago

charlespax commented 9 years ago

Some components appear to be more available than others. Maybe we should change some values to reflect what is out there. Here are some possible changes

Tsillen commented 9 years ago

I would leave it as tbd (to be determined) or a value with quite a big margin (if it does not effect the system). example: 500R +-10% then just have diffrent BOM's for the hardware revisions and chose a value that fits in this region that is currently the cheapest available.

Because even an 500R 1% resistor can be 495-505R so it does not matter =)

charlespax commented 9 years ago

That's a good point. I'm not sure how the manufacturer would want it though. I am assuming they want explicit instructions, so they don't have to make decisions. We'll sort it out with the manufacturer.

samchoy88 commented 9 years ago

we usually apply ±5% for resistor and ±10% for capacitor see below standard resistor and capacitor value http://ecee.colorado.edu/~mcclurel/resistorsandcaps.pdf

In the circuit, may be we change the 53.6R resistor to 51R appear to be more available. image

charlespax commented 9 years ago

Cool, that should be good. I was listing 1% on the resistors for quoting because the price difference at the electronics market was so small. I imagine 10% is fine for all the capacitors. For the resistors I wonder if we should use higher precision resistors for the thermocouple sensing portion and anything that may affect the readings.

As it stands now there is no calibration routine, so it could be good to just make the thermocouple sensing portion as accurate as we reasonably can. This would ensure that all the units would similar calibration numbers. If the sensing portion on each device is very consistent, we may be able to flash each one with the same data and not have a calibration routine.

We may also have to have a 1% or high precision resistor on the LCD, so each device has the most similar backlight levels. Moving from 53R to 51R should be fine. We should just keep the LCD resistors very consistent.

charlespax commented 9 years ago

Closing this. Done.