74ls47 and 7 Segment

[watzmann]

Hi All ,

i have attached the following image for my schematic , but i actually have alittle problem , that some selection when i select produce digits cannot displayed correctly on the 7 segment due to the limitation of the 7 segment from 0 to 9

so i need to add more 7 segment to accept higher number like 14 and 16 .....but i don't know how to wire the new 7 segment could you help me please

 

[Dean Huster]

For additional digits, simply duplicate what you have for each additional digit. For any simple configuration of a 7447/74LS47, you need not connect anything else on the '47. If you need leading zero blanking, connect the BI/RBO of the more-significant stage to the RBI of the next-least-significant stage. The most significant stage will have the RBI connected to ground (LOW) to start the blanking. If RBI is LOW, then that stage will blank a zero. If a stage blanks a zero, its BI/RBO output will go LOW, signalling to the next least-significant stage that it has blanked and that it can blank if it has a zero. The lest significant stage usually has the RBI connected to +5v (HIGH) so that it never blanks, assuring you that the readout is "live". BI/RBO is an input and an output. If you force BI/RBO LOW, that digit will blank regardless of the ABCD input. This can be handy for flashing a display for a warning, such as an overrange condition. LT is normally connected to a HIGH. Bringing LT LOW forces all segments ON as a "lamp test". I don't like floating inputs. Even though the '47 has pretty reliable output with these control input floating, I still make sure they're HIGH if I need them to remain so by connecting them to +5v. Be aware that any ABCD input that you do not must absolutely MUST be connected to a LOW or your display will not produce the correct readout.

Dean

 

[Papabravo]

You also have the problem of converting binary to decimal unless you intend to display 4 binary bits as hexadecimal. The short list for binary to BCD conversion is:

1. Decoding ROM
2. Decoding PLD or FPGA
3. Microcontroller

 

[blueroomelectronics]

A pair of small microcontrollers would simplify the project. And you could reduce the amount of data lines between them to 1 + GND

 

[Dean Huster]

One wonders how it is that we managed to invent radio, television and put a man on the moon without the help of microcontrollers. I hear they'll also cure AIDS, cancer and bunions. How quickly will this project get finished if the OP has to drop everything, run out a buy the µC, programming hardware and software and spend untold amounts of time learning all about them? Myself, I'm an ELECTRONICS experimenter, not a code slinger.

Back OT, my favorite decoder/driver is the expensive and difficult-to-find 9368, an all-in-one decoder, driver, current source, hexadecimal displaying cutie that eliminates the seven current-limiting resistors required for the LED segments. There are also a couple of CMOS D/Ds that will display hex. The 7447 will display input above 1001b, but only as cryptic characters that need decoded in their own right and 1111b displays as a blank character (not a blanked display because with a LOW on the RBI and 1111b as the data input, the BI/RBO does not go LOW).

And sorry about the curmudgeonly outburst above. I just get tired of the software-will-save-the-world glimpse of life that I'm constantly getting.

Dean

 

[blueroomelectronics]

I'm sure NASA would have loved a microcontroller if one was available, they built the AGC (Apollo Guidance Computer) considered one of the first embedded computers.
https://en.wikipedia.org/wiki/Apollo_Guidance_Computer
When working with digital electronics microcontrollers are the way to go, even the venerable 555 has been bumped in favor of a more accurate, lower parts count and often cheaper microcontroller counterpart.
Here's the answer to the OPs question, but he won't like the price.
TIL311 a nice 1970s part.
PS I think most of the over 40 crowd here are Curmudgeons, myself included.

Edit: if you read watzmann's older posts he has a 16F877A microcontroller...
**broken link removed**

 

[Dean Huster]

The TIL311 is the best-int-the-world all-in-one package. I love them, too. But yeah, they're expensive and impossible to find these days.

Bill, the 8080 was many years into its production and yet couldn't be used in NASA or military applications because it wasn't MILSPEC. An electronics engineer friend who worked for Texas Instruments in the design of the Harpoon missle guidance system had to use TTL centered around the 74184 ALU to do all the guidance math. Yes, using a processor would have been nice, but they just didn't have the kahunas to handle the rigors of aerospace yet.

Dean

 

[blueroomelectronics]

I remember RCA produced the 1802 using Silicon on Sapphire so they could send it out to space.

Dean, any tips on getting an article published in a magazine?

 

[Hank Fletcher]

Dean, any tips on getting an article published in a magazine?

Sorry to interupt, but I might have an idea, although not specific to electronics literature. I'd contact the editor of the magazine, preferably by phone. It's easier to "sell" your article through talking with someone - I wouldn't even bother trying to cold-email an editor. Talk to them first, and ask if you can send along a sample of your work.

The number one rule of sales (and you're selling your article) is not to give up, especially when people say no. You may have lost that customer/editor, so maintain your dignity and move on to the next one. If patterns emerge in reasons for why people are saying no, take those into account and adjust accordingly, but do not give up just because the first or ninth person says they can't make it happen.

Editors don't run magazines, unless you're talking scholarly journals. Ad sales people run the show, because the number of pages in the magazine is dictated by how many ads they can sell, which dictates how much content a magazine can publish in any one issue. I'm just mentioning this to give you some insight into the key factor that effects editor's decisions. It might not be that your content isn't good enough or that it doesn't suit the wishes of the editor. It might just be that the editor has a lot of people submitting articles for publication. It's very rare that a magazine doesn't have enough resources for content. Remember, you're asking the editor to sacrifice money-making ad space to publish your article. Sure, people might buy the magazine specifically to read your article or their favourite regular feature, but what they pay for the magazine is a pittance in comparison to the money coming in from ads. Of course, nobody sees the ads if there's nothing to read in the magazine, but for whatever reason that bit of logic tends to be discounted in the content-decision-making process.

You mean you want an article published that you've written, right? That's better odds than trying to find a writer and editor who'll both take interest in what you've got. Remember, as informative and interesting as your article may be, you're essentially asking for free ad space (of a sort), so be prepared to make a strong case.

 

[Nigel Goodwin]

Dean, any tips on getting an article published in a magazine?

I would suggest writing an article they really want, so you don't need to sell it, they will instantly desire it.

Just a question of finding something they want?.

 

[jpanhalt]

Dean, any tips on getting an article published in a magazine?

Dean certainly has the experience to advise on electronic magazines, and as Hank says, it depends on the nature of the magazine.

Scholarly journals go through a peer review process -- at least most of them do. If you submit and get rejected, don't worry. That is very common, even for experienced authors. You can appeal to the editor with your reasons, and the ed. will usually ask for you to submit something revised and addressing the reviewers comments. It can alos help to get a little support from someone wo has published. Just remember, the peer reviewers are not without bias or fault. The editors know that and will consider it, if approached correctly.

If it's a pulp magazine, then the process is certainly different. As suggested, contacting the editors first may be a good start.

There is a third option, which is to present your material as a new product release. Advertiser-supported magazines are often quite liberal in what they will allow to be put in a new product release, and the ones I have dealt with are usually free.

Whatever happens, don't get discouraged by a few rejections. This is one of my favorites from Schultz (Peanuts):

John