Hi David,
WOW! thanks, I will review it fully and get the parts purchased asap. I will bread board the circuit. The 8 x 7 segment displays have been wired up in multiplex format and I have written the software, based on my use of a Wemos D1 R2 board, all that I have to do is write an interface between it and this new circuit. If I have any further questions is it ok to contact you for help? Regards, Christine P.S. If you look at the “Clocks! Picture Sharing” post you will see the clocks I have completed so far. From: [email protected] <[email protected]> On Behalf Of David Forbes Sent: Tuesday, November 5, 2019 6:40 PM To: NeoNixie <[email protected]> Subject: Re: [neonixie-l] Re: 7 Segment Common Anode Display Here is a schematic diagram that I just whipped up. It uses the SPI signals to shift data into the anode and cathode drivers. The software needs to write two bytes (digit then segments) to the SPI port, then write LOW then HIGH to the LD/ signal. The digit byte must have one bit low to select a digit. On Mon, Nov 4, 2019, 9:48 PM Christine Thompson <[email protected] <mailto:[email protected]> > wrote: Hi David, Thanks for the information. My last clock used 8 X ICL/1-1-8 VDF displays using the MAX6921 chip and works fine, silly me to assume that the same chip would also work with 7 segment displays, started to worry when I noticed in the MAX6921 datasheet that the minimum output voltage was 8V. In all the clocks I have made I have used either the MAX6921 multiplex method or K155 IC chip Direct drive method. So I need to go back to basics for this clock. I can certainly purchase the shift registers and Octal buffers from E-Bay, however in the meantime could you suggest a link to an article / document that describes the basic method of how this system is constructed. Regards, Christine From: [email protected] <mailto:[email protected]> <[email protected] <mailto:[email protected]> > On Behalf Of David Forbes Sent: Tuesday, November 5, 2019 4:48 PM To: NeoNixie <[email protected] <mailto:[email protected]> > Subject: Re: [neonixie-l] Re: 7 Segment Common Anode Display There is no reason to use a fancy Maxim chip for an LED display. Two 74HC595 SPI shift registers and two 74AC245 octal buffer chips will do the job. One for the anodes, one for the cathodes. On Mon, Nov 4, 2019, 3:41 PM gregebert <[email protected] <mailto:[email protected]> > wrote: The Maxim part you mentioned is for VFD's, and it looks like it can run as low as 8V. If you use it to drive the anode of your LEDs, you run the risk of exposing the logic driving the cathodes (segments) to roughly 6 volts (the LED has about 2V of forward bias). If the Arduino has 5V-tolerant I/O pins, you will have problems because there will be a current path through the LED to the 5V supply even if your LED is off; this is the parasitic-diode path in the IC that forms part of the ESD protection network for pins. Before going any further, do you have a datasheet for the LEDs ? You need to know how much current is required when running multiplexed in order to select the correct driver IC. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected] <mailto:[email protected]> . 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