6 Digit HT1621 LCD Display Module on 5V with a 3.3v Micro controller.

Hello everyone here's my dilemma. I have a 6 digit Display module that only works on 5v But it said i can run it as low as 4.2v. Problem is I'm would like to use a ESP8266 on it which only runs on 3.3v no higher. I try to run the display on 3.3v and it freaked out. So i'm not sure how to boost the Power from 3.3v to 5v with what i have now. I don't have much so not sure what to do. Can someone please help me to figure this out? Also I was wondering maybe the display won't work if it's 3.3v logic either I'm not sure. Here is a link on the display.


The datasheet specifies a minimum logic HIGH voltage of 4.0V but it would be surprising if it did no operate with the 3.3 V ESP8266 level. Given that the display is input only. It should be quite safe to hook it up and try is. Just ensure that the display is always powered when the ESP will be.

I haven't tried it with a ESP yet. Just wanted to get some advice on what is should do before i try it. I have tried to step down the vcc to 3.3v and it freaked it out. So i don't know if 3.3v logic will be okay or not Sense i have to put at least 5v on the power side.

Well, the display clearly contains a logic IC which has sufficient output capability to drive the segments but (presumably CMOS) presents a negligible load on its inputs and will not feed any current back into them but will present a ground load to them if its power is turned off, which is the reason for my previous warning.

Now while most CMOS logic is specified to require 1/3 Vcc LOW and 2/3 Vcc HIGH logic levels on its inputs, unless it is a Schmitt input with particularly large hysteresis, it will generally switch at close to half of Vcc or around 2.5 V, so your 3.3 V logic should drive it OK.

It should be safe to do, and it should work.

Hello Paul__B thank you. I will try in the next 2 days if this will or will not work. I'm finishing up my other project for that has temperature logging with mysql I'm almost done and then i'll try out this one and see if a ESP8266 will work on it or not. I'm putting 5v and a 3.3v regulator on it for the ESP and just keep the LCD at 5V. Hopefully this will work. I'l post a update in a couple of days.

Again thanks for the advice.