a d converter


Posted on Feb 6, 2014    12549

This is the first draft of the pH to 1-Wire converter schematic, and some of the component values are still missing. The original circuit runs on 12 VDC, but since the A/D converter IC must be supplied with 5 VDC only I want to scale down the circuit, so that 5 V is the maximum voltage present. I assume I would have to tweak some resistor values i


a d converter
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n order to make the circuit run at this lower supply voltage, but I haven`t looked into the details yet. I`ll post an updated schematic and the calculations later. The original idea was to use a 1-Wire A/D converter with built-in 1-Wire digital interface, but the one I found was not recommended for new designs. This is what Maxim writes about the DS2450 A/D converter: This product is Not Recommended for New Designs. Some versions may be No Longer Available or being discontinued and subject to Last Time Buy, after which new orders can not be placed. Also known as NRND`. Most of the other A/D converters I found at Maxim had another interface, but the main IC on the soil moisture sensor board from Hobby Boards also converts analog signals to digital and that`s a DS2760. The updated version is called DS2762, which is the one that I have used in the new circuit. The DS2760 on the soil moisture sensor board measures current, but the IC also has a voltage input pin. The IC is actually a High-Precision Li+ Battery Monitor With Alerts` as Maxim calls it. The idea is to only use the voltage input pin and 1-Wire interface to get a popular, and cheap, A/D converter, with high input resistance. Since the DS2762 operates on 5 VDC, the ground reference for the amplifier section should be changed to 2. 5 V instead of 7 V in order to use the entire input voltage span of the A/D converter. The 7 V in the original circuit was meant to be...




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