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Power Supply

A project log for RPi Telegraph

The 19th century texting device meets the 21st century

ed-danisEd Danis 05/25/2015 at 02:130 Comments

I've learned (luckily not the hard way) that I need to limit the current going to the solenoids to avoid damaging the sounder. There are a number of references, but I have not yet found a definitive source on what the proper current should be. Each sounder has a known resistance, so I'm going to experiment with a 12VDC Power Supply and will move a way from using the relay shield and replace it with a MOSFET. More to come.

Power SupplySounderCurrent Limiting ResistorCurrentWorked?
12V20 Ohm100 Ohm98 mAY
12V20 Ohm150 Ohm72 mAY
12V20 Ohm220 Ohm50 mAN

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