Need help converting Vfd to led - Page 1
Forum section: electronics / repair

author: Thatcrippledguy
author_rank: Newbie
timestamp: January 11, 2020, 05:02:56 pm
content: I have been working on a digital dash from a chevy s10 blazer.It is a vfd instrument panel, I went through it and got it working to find the speedometer vfd glass is broken. I have been doing a lot of searching with not much luck. I did find a member on this forum Satbeginner who did a write up on ithttps://www.eevblog.com/forum/repair/fluke-45-vfd-display-broken/I still have some questions.I have a digital led clock that I pinned out that I am thinking of using to do testing. Hoping to use vfd driver to power the led.1) I searched google and could not find a data sheet listing the components. Not sure if I am searching the wrong place or wording.2) Satbeginner post (link I posted) used 470 ohm resistor, I am not sure wattage to use? Should the be placed positive or negative side? Will those resistor ohms work in my situation?3) where do the diodes need to placed?4) out of curiosity there is a thin white component, what I could find looks like a resistor on the board. Has 11 pins, searched the numbers printed on it with no results. "16138816" I will try to attach pictures. I would prefer not have to de-solder it to get the ohm readings.Buying a new/used working dash is more than would like to spend on this vehicle. can't seem to attach more pictures to this post if needed will post more.Any help will be much appreciated.

author: ebclr
author_rank: Super Contributor
timestamp: January 11, 2020, 10:40:14 pm
content: Do you know typical tension and current of VFD and LEDs, they are rough different, I guess is not feasible what you want to do, VFD and Leds are extremely incompatible because one is a tube work with high tension and low current, the other is a semiconductor low voltage and relatively high current. The easiest way to do this is to look at driver interface, If you know what is the VFD controller, and is one with a known Datasheet, you may intercept the display commands and data and send to a led driver using a microprocessor like PIC, Arduino or even 8051.Another path is to use a lot of transistors, and do a level conversion ( tension and current )

author: Thatcrippledguy
author_rank: Newbie
timestamp: January 12, 2020, 04:25:30 am
content: Thank you for your reply and help. My knowledge of circuit boards is limited, mostly basic testing, inspection, replacementHow they work, I am still learning. Building a led driver might be over my head right now..What I was following was an another member on this forum Satbeginner who converted a vfd to led using diodes, resistor,and npn transitors this is his post: (which looked like it might be more in my capability than building a driver and adapting it to the current instrument pannel, though it might be harder than it sounds?)https://www.eevblog.com/forum/repair/fluke-45-vfd-display-broken/As the member wrote"""" I use the diodes (1N4148) to remove the negative -32V, now only using the +5V part of the signal, followed by a NPN switch transistor to drive the Common Cathode Digit´s.The LED current is supplied by the VFD-driver chip, again, negative voltages are removed by the serial diodes, current limiting is done by the 470 Ohm resistors. (appr. 6mA)The reason I remove the Negative voltages, is to protect the display LED´s against reverse breakdown.,""I do not have a datasheet, I tried googling, a couple of websites, the board manufacturer and was unable to find anything? . Though I may have been using the wrong words. That was one of the other things I also needed help on.

author: ebclr
author_rank: Super Contributor
timestamp: January 12, 2020, 06:24:07 am
content: http://www.princeton.com.tw/en-us/products/displaydriveric/vfd.aspxhttp://www.agspecinfo.com/pdfs/P/PT6315.PDFHere you can see a VFD controller datasheet, You use this as a general reference if you wanna go on the transistor patch Way, It's possible to do something with transistor/resistor and diodes, but you need to understand the structure of you controller

author: Thatcrippledguy
author_rank: Newbie
timestamp: January 24, 2020, 08:48:54 pm
content: Thank you for the reply and information. I am not sure what the two links you provided applied to doing the level conversion with the diodes, transistors, and resistors. Are they for intercepting the signal to use the microprocessor? I don't know enough to try that route yet, I am trying to learning.I went with diode, transistor,resistor path. With a lot of help from another member Satbeginner and who inspired me to attempt this.Quotewhat is a lot of transistors, I only used two for testing, maybe I didn't use enough? I got it to work using the clock display(had one not working) for testing. All lit up like it should have ""1,8,8""; except one missing lead, I broke the circuit board copper connection during rewiring. Waiting on new 3x 7 segment led displays to finish my testing and building of replacement board to fit in vfd's place. If it all works I may make the whole vfd digital dash into an led digital dash.I would like to learn using microprocessors to make a smart vehicle with a better instrument cluster with more information, and build a custom ecu for better engine control and adding some better features such as fuel injected probably using a "megasquirt" kit. Though still a lot more to learn before I attempt.

author: Thatcrippledguy
author_rank: Newbie
timestamp: January 24, 2020, 09:19:20 pm
content: More pictures of the layout and schematics I am following.( not whole schematic of every pin, they just repeat). I am still seeing to much voltage to the leds around 5v. I have 8 to 10 volts coming from circuit board. So I still have some adjustments to make to get it to the 3 volt max the leds are supposed to be seeing.

author: james_s
author_rank: Super Contributor
timestamp: January 25, 2020, 12:02:29 am
content: LEDs are current driven, not voltage. The voltage across an LED will vary some depending on the current being pushed through it but it's the current you want to be looking at and size the resistor appropriately to result in the desired current at the voltage you have available.I think the transistors are probably a reasonable approach, other options would be to work out how the controller is driven and possibly intercept that and decode it with a microcontroller that can then spit out whatever you need to control any display you want.