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Vampire05
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Joined: 06/12/2020
Location: Germany
Posts: 88

Posted: 08:22pm 20 Apr 2022

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Hi Guys,
In the Micromite manual it says that for more stable ADC results pin 27 and 28 should be connected to a good voltage source. What would be a "good" way to realize this?
A 3.3v LDO, reference voltage ic,....?

Greetings
Artem

Amnesie
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Joined: 30/06/2020
Location: Germany
Posts: 719

Posted: 08:54pm 20 Apr 2022

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Hello,
a 3V3 LDO isn't a good reference voltage. Please don't do this. If you don't want to overengineer things, a LM336-Z2,5 reference voltage will do the trick, they are cheap and available.

Da du auch aus Deutschland bist, schau mal bei Reichelt. Die haben genug Spannungsreferenzen.

Greetings
Daniel

Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 8298

Posted: 09:00pm 20 Apr 2022

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Connect a LM4040 3V reference chip to the REF pin of the PicoMite. This chip is similar to a 3V zener in usage but is much more accurate and stable. Then set it up using
OPTION VCC 3
in a program (it isn't saved).

The PicoMite normally assumes that the supply voltage is 3V3 and uses this as the voltage reference for the ADC. Carrying out the above changes the reference voltage to 3V.

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

Vampire05
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Joined: 06/12/2020
Location: Germany
Posts: 88

Posted: 09:28pm 20 Apr 2022

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Thank you Guys,
Danke dir Daniel!

Is it possible to Use REF Voltage on the Micromite (not Picomite)?

Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 8298

Posted: 09:39pm 20 Apr 2022

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Yes. It connects to the VREF pin. On the Micromite you will need a resistor from 3V3 to the VREF pin then a LM4040 3V to ground. Using it isn't quite as straightforward though as it doesn't have OPTION VCC. See page 37 of the Micromite manual.

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

Vampire05
Regular Member

Joined: 06/12/2020
Location: Germany
Posts: 88

Posted: 06:18am 21 Apr 2022

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Thank you Mixtel90

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