Open-collector question

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Well-known member
Hi guys,

Just wondering about the following. In the past, we've discussed how the DS18B20 is a open collector device, allowing you to power the thing at 5V and communicate at 3.3V (by using a pullup resistor on the data line to 3.3v). Based on the description of the DHT22 (see p.5 here:, it appears that the AM2303 is no different. Thus, would it be possible to power the AM2303 at 5VDC but communicate at 3.3V by pulling up to 3.3V instead of 5V?
From your pdf file it looks like you could power it with 3.3v So I would assume your PU could be 3.3v
Sounds good.
I connected ds18b20 at 3.3v (3 wire) over 10m of cat5 cable and it worked but was considering your method. Good to know it works.
OK, tested it tonight - the version of a DHT22 I used appears to be an open-collector device - it could be powered at 4.7V (or whatever the VIN is on a Teensy 3.0) while the pullup resistor for the data line was attached to the 3.3V regulated output from the Teensy 3.0. I used pin 13 and confirmed operation for the device at VCC=VIN as well as VCC = 3.3V
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