David16962
Posts: 77
Joined: Thu Aug 11, 2022 7:52 pm

[SOLVED] Replacement chip for obsoleted DS18B20

Wed Nov 23, 2022 10:47 pm

Any pointer to replacement chip for DS18B20 which is marked as obsolet, no stock or high price on two major multinational distributors I just searched.

I am starting to build a project, on Pico or RPI or both, using Circuit python, micropython or python, with multiple temperature seensors in near by area. It would be easy to use DS18B20 for simple one wire bus connection. Sensing range -10 to +90 celcius, accuracy around 0.5 clecius.

TIA
Last edited by David16962 on Thu Nov 24, 2022 3:27 pm, edited 1 time in total.

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neilgl
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Location: Near The National Museum of Computing

Re: Replacement chip for obsoleted DS18B20

Wed Nov 23, 2022 11:10 pm

Millions available on eBay cheap ??

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rpdom
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Location: Chelmsford, Essex, UK

Re: Replacement chip for obsoleted DS18B20

Wed Nov 23, 2022 11:23 pm

DS18B20+ looks like it might be the current version.
Unreadable squiggle

MiscBits
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Re: Replacement chip for obsoleted DS18B20

Wed Nov 23, 2022 11:48 pm

Just be aware the accuracy drops above 85C to +/-2C at the extreme points and +/-1C at the top of your range.

Some of the cheap offerings off eBay I have bought previously have had differences between them of +/-5C (yes 10 degrees between extreme devices). Buy from a reputable supplier or spend time calibrating them in software...

pidd
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Re: Replacement chip for obsoleted DS18B20

Thu Nov 24, 2022 1:07 am

There is an extensive article on the clones and their associated problems https://github.com/cpetrich/counterfeit_DS18B20

ame
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Location: New Zealand

Re: Replacement chip for obsoleted DS18B20

Thu Nov 24, 2022 1:20 am

neilgl wrote:
Wed Nov 23, 2022 11:10 pm
Millions available on eBay cheap ??
They are undoubtedly fake.
Hmm. What can I put here?

cleverca22
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Joined: Sat Aug 18, 2012 2:33 pm

Re: Replacement chip for obsoleted DS18B20

Thu Nov 24, 2022 7:03 am

when you try to pull up the ds18b20 page on sparkfun, you get https://www.sparkfun.com/products/14049, the page for the MAX31820

protocol is identical, but it must be powered within 3.3 to 3.7v, no problems for an rpi

David16962
Posts: 77
Joined: Thu Aug 11, 2022 7:52 pm

[SOLVED] Replacement chip for obsoleted DS18B20

Thu Nov 24, 2022 3:25 pm

Many thanks for reply. The github reading is very detailed.

After more reading, MCP9808 looks nice. One USD more expensive (from same well known supplier), better accuracy at 85 to 100 celcius. Eight can be connected on same I2C bus.

±0.5°C (maximum) from -20°C to 100°C
Operating Voltage Range: 2.7V to 5.5V
I2C with jumpers for 8 address on the same bus. 0x18 + (0..7)
Automotive Electronics Council AEC-Q100 qualification

http://www.adafruit.com/datasheets/MCP9808.pdf

4.95 USD https://www.adafruit.com/product/5027
3.95 USD https://www.adafruit.com/product/374

d_older
Posts: 136
Joined: Mon Jun 25, 2012 5:04 pm
Location: East Yorkshire, UK

Re: [SOLVED] Replacement chip for obsoleted DS18B20

Fri Nov 25, 2022 12:09 am

Hi David16962,

Just a couple of questions re DS18B20 vs MCP9808.

1) What sort of wire length are you looking at - you state "in near by area" ? I2C was designed for inter- device links within or to adjacent PCBs within a unit. The recommended max. length is around 1m. Obviously 1-wire has a significantly greater maximum wire length.

2) Possibly more importantly, where have you seen that the DS18B20 is obsolete ( or even depreciated ) ? According to Maxim/Analog Devices the part is "Active in Production"
Ref: https://www.maximintegrated.com/en/prod ... 18B20.html

Obviously the MCP9808 does have greater accuracy.

Regards,
Dave

David16962
Posts: 77
Joined: Thu Aug 11, 2022 7:52 pm

Re: [SOLVED] Replacement chip for obsoleted DS18B20

Fri Nov 25, 2022 12:23 pm

Hi Dave,

Many thanks for helpful advises.

1. I am DIYing a Multi depth soil temperature sensor to measure with as per WMO recommendations, at soil depth of 5, 10, 20, 50 and 100 cm. If RPi Pico is placed at end, I2C length is one meter. Some web information says 1 meter at 100,000 KHz, 10 meters at 10,000 kHz even using high capacitance cable. Distance is longer with low capacitance cable. Weather is slow changing data hence low I2C speed is fit for job.

http://www.mosaic-industries.com/embedd ... ifications

In worst case, Pico can be placed at middle using two I2C ports, each runs 0.5 meter.

2. It is marked as "RED LC Obsolete" icon in Mouser. Yes, next time, I should double check information from the factory vs. distributor.

https://www.mouser.co.uk/ProductDetail/ ... ViXg%3D%3D

Mouser has three icons, green NEW product, YELLOW LC and RED LC (for the DS18S20). Mouser explains, quoted, "As a leader in new product introductions, Mouser eliminates unwanted surprises by identifying Not Recommended for New Design (NRND) and End-of-Life components. Clearly labeling lifecycles on thousands of products helps avoid out-of-stock issues, project delays and costly redesigns caused by using old, out-of-date components – yielding a time-to-market advantage."

Time ago, I got email from mouser stating a chip that I brought has newly issued factory notice, stating it is planned "end of life" or "upgrade to B version" at certain date. This is useful for professional engineers who design "production-run products".

https://www.mouser.co.uk/lifecycles/

hippy
Posts: 12693
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Location: UK

Re: Replacement chip for obsoleted DS18B20

Fri Nov 25, 2022 6:24 pm

rpdom wrote:
Wed Nov 23, 2022 11:23 pm
DS18B20+ looks like it might be the current version.
Correct. The original "DS18B20" became the "DS18B20+" some time ago, AFAICT to comply with RoHS.

Most people just refer to this latest version simply as "DS18B20" but some suppliers and distributors differentiate the two, have "DS18B20" as obsoleted or superseded by "DS18B20+".

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