Using a TM1637 for a large 4 digit display. - Page 1
Forum section: electronics / beginners

author: IY3775
author_rank: Newbie
timestamp: February 25, 2019, 08:32:36 am
content: The TM1637 4 digit 7 segment display module comes with a tiny 0.5" display attached. Now I want to build a large 7 segment display with red LED strips, remove the 0.5" display and attach the large one. I don't think the TM1637 will be able to handle the load, question is how do I connect my own large display to the module?http://cloud.tapatalk.com/s/5c73a808a128c/Datasheet_TM1637.pdfSent from my Mi A1 using Tapatalk

author: janoc
author_rank: Super Contributor
timestamp: February 25, 2019, 09:26:34 am
content: Depends on the display you have. If your large display can fit within the 50mA or so capability of the chip (many largeish ones can, 50mA is a ton of current for a LED), then you can just swap them and it will work (modulo things like common anode/cathode differences - make sure your display has the right setup!)If you need more, then you will need to either look for a driver with more current capability or use some transistors as drivers to boost the current capability.

author: IY3775
author_rank: Newbie
timestamp: February 25, 2019, 09:34:23 am
content: I'll be making my own display with LED strips, it's going to draw a lot of current. How to I add transistors to this setup? A diagram is much appreciated.Sent from my Mi A1 using Tapatalk

author: SteveyG
author_rank: Unknown
timestamp: February 25, 2019, 11:20:36 am
content: The TM1637 is designed for common anode displays. You will need to buffer the outputs from this chip with external transistors to allow you to drive your LED strips from a presumably higher supply voltage since the maximum input voltage is only 7V.

author: IY3775
author_rank: Newbie
timestamp: February 25, 2019, 11:23:16 am
content: Quote from: SteveyG on February 25, 2019, 11:20:36 amWill a uln2005a work in this application? Could you provide a diagram if I have to use individual transistors?Sent from my Mi A1 using Tapatalk

author: janoc
author_rank: Super Contributor
timestamp: February 25, 2019, 09:31:02 pm
content: If you want to drive LED strips, there is not much point in trying to reuse TM1637 which isn't designed for that. Without knowing how many LEDs, how are they going to be connected, what type of LED strip ("dumb" one, "neopixels", whatever), what current/voltage, etc. it is impossible to tell you whether uln2005a or whatever else will work. Draw some diagrams so that we know what you are trying to do, people don't read minds here.

author: IY3775
author_rank: Newbie
timestamp: February 26, 2019, 03:23:35 am
content: Quote from: janoc on February 25, 2019, 09:31:02 pmThe reason I want to use TM1637 is I can't use 12 I/O pins from the Arduino, (& they're cheap and easy to work with).I'll be using regular 12V 2835 red LED strips, which may take about 150ma on the longest segment for each digit, half for the smaller segments, so about 500ma per digit. The display would be in common anode. Will it work as below?:Sent from my Mi A1 using Tapatalk

author: kjr18
author_rank: Regular Contributor
timestamp: February 26, 2019, 05:51:04 am
content: You still need more transistors, one for every segment line, that would be a total of 12 transistors, 8 for segments, 4 for digits.

author: janoc
author_rank: Super Contributor
timestamp: February 26, 2019, 09:58:39 pm
content: As kjr18 said, you must have a transistor for each segment too. The IC cannot handle neither the 12V (minus whatever drop the strip has) nor sink 150mA of current - according to the datasheet it can sink only 50mA so it would be overloaded 3x and most likely release the magic smoke.You will also need a current limiting resistor in the base of each transistor or you will likely blow them.

author: IY3775
author_rank: Newbie
timestamp: February 27, 2019, 01:45:15 am
content: Quote from: janoc on February 26, 2019, 09:58:39 pmCould you show me how to connect transistors to each segment then? Is it npn or pnp?Sent from my Mi A1 using Tapatalk

author: janoc
author_rank: Super Contributor
timestamp: February 27, 2019, 09:02:26 pm
content: For each segment you will need an PNP transistor (or an P-channel MOSFET), emitter/source to the segment (LED), collector/drain to ground. The reason for this emitter follower arrangement is that your segment outputs of the IC are active low (it is meant for a common anode display). Alteratively you could use NPN transistors but then you would need two per segment - the first one would be inverting the driving signal from the IC for the second one.You need to find transistors that can handle the current, of course, but 150mA per segment isn't that much.

author: IY3775
author_rank: Newbie
timestamp: February 28, 2019, 02:16:06 am
content: Quote from: janoc on February 27, 2019, 09:02:26 pmThx, and the gate/ base to the corresponding pin of tm1637?Sent from my Mi A1 using Tapatalk

author: janoc
author_rank: Super Contributor
timestamp: February 28, 2019, 07:45:21 pm
content: Quote from: IY3775 on February 28, 2019, 02:16:06 amYes, of course.

author: fawad
author_rank: Newbie
timestamp: February 02, 2022, 01:09:23 pm
content: any try to run big seven segment disply with tm1637 driver. if any one kiindly give circuit diagram, i try to run 3/2 inch comman anode segment

author: Genilson Silva
author_rank: Newbie
timestamp: September 17, 2024, 04:57:36 pm
content: Hi friend, you were successful in creating a power interface to use a led strip with the tm2637 chip