Peter Wright
Posts: 4
Joined: Mon Oct 21, 2013 9:59 am
Location: Heidelberg Germany/ Newcastle UK

5v to 3.3 Level shifter

Mon Oct 21, 2013 10:44 am

Hi My name is peter I am a Senor design engineer and have a solution for some of you !
You have a 5 v device that is sending some 5V TTL Level out but the PI accepts only 3.3V you think you need a level shifter because everyone is talking about them dont you ?
A Solution out of the profeshional cook book take a 3.3v Zenner diode and connect it to gnd the other end you connect to a 6.8Kilo ohm resistor , the other end of which you connect to your 5 v output from your 5v device , now go to the summing point between the zenner and the resistor if this has changed to 3.3v congratulations you have made a level shifter with 2 components. if something is wrong change the direction of your zenner cathode ring up to summing point , this method is perfect for very fast signal change and most problems on pi forums concern inputs to the pi not outputs or ?

Regards Peter
P.s as an old fart I think the guys who developed the pi are Supercalafristicexpialerdocious !!keep up the good work

Posts: 72
Joined: Sun Nov 11, 2012 8:14 am

Re: 5v to 3.3 Level shifter

Mon Oct 21, 2013 1:21 pm

Zener voltage limiters have often been used in Pi projects in the past and are also often recommended for beginners as they are easy to use with protoboard/plugboard for quick experiments. However, their major disadvantage is that they are uni-directional and the Pi's GPIOs often require a bi-directional solution.

4 and 8-channel bi-directional voltage converter boards are now available so cheaply that they are probably cheaper than discrete components for people who purchase in small quantities. See ... 5aebfc73f5 for example.

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