It is currently Thu Sep 20, 2018 10:53 pm

 All times are UTC - 7 hours

 Page 3 of 3 [ 34 posts ] Go to page Previous  1, 2, 3
 Print view Previous topic | Next topic
Author Message
 Post subject: Re: LPT EPROM Reader?Posted: Sun Sep 10, 2017 12:40 pm

Joined: Sun Apr 13, 2008 11:12 am
Posts: 7532
Location: Seattle
One thing that immediately pops out to me:

The LM317 has a certain amount of current that flows out of the ADJ pin (50-100µA). Your voltages will be a little bit higher than intended because it wasn't taken into account.

Also, Vin from the parallel port might be 3.3V instead of 5V. You should check, because it'll change the math.

But that's not what you asked.

The page you found does this:
• bcurrent = IC ÷ hFE
• baseresistor = (Vinput - VBE) ÷ (3·bcurrent)

He's added a margin of 3 safety factor. Which should account for the difference between the Rb of 430kΩ that you found and the 143kΩ he recommends. I forgot to mention that β is a function of both temperature and the collector current, so derating by a factor of 3 is a reasonable good way to ensure that it'll stay in saturation regardless of the current state of the transistor.

Note that the BC547's Vcesat is probably smaller than the 1.4V you're using. The exact value will change the value of Rc you want to use.

Top

 Post subject: Re: LPT EPROM Reader?Posted: Sun Sep 10, 2017 1:35 pm

Joined: Wed Apr 07, 2010 1:14 am
Posts: 484
Location: Iran
By using the bottom calculator, 120K seems to be a good value for R11 :
Vbe : 0 V
hFE : 110
Ic : 0.001 A
Vi : 3.3 V

By using the above calculator, 100K seems to be a good value for R14 :
Vbe : 0.7 V
Vce : 0.25 V
hFE : 110
RL : 4700
Vcc : 5 V
Vi : 3.3 V

Top

 Post subject: Re: LPT EPROM Reader?Posted: Mon Sep 11, 2017 12:31 pm

Joined: Wed Apr 07, 2010 1:14 am
Posts: 484
Location: Iran
I have tested it for a few times and it seems to work fine.
27C080 Read time : 40 Seconds
27C080 Write + Verify time : 40 + 60 Seconds
OS : Windows XP

When I started this project a few weeks ago, I didn't have any idea on how to make a programmer.
I couldn't be able to do it without lidnariq help, thank you very much.
I have learned a lot from this project.

 Attachments: EPROM Programmer.zip [324.97 KiB] Downloaded 38 times
Top

 Post subject: Re: EPROM LPT Programmer?Posted: Mon Sep 11, 2017 12:36 pm

Joined: Sun Apr 13, 2008 11:12 am
Posts: 7532
Location: Seattle
You're welcome!

Top

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 3 of 3 [ 34 posts ] Go to page Previous  1, 2, 3

 All times are UTC - 7 hours

#### Who is online

Users browsing this forum: No registered users and 3 guests

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum

Search for:
 Jump to:  Select a forum ------------------ NES / Famicom    NESdev    NESemdev    NES Graphics    NES Music    Homebrew Projects       2018 NESdev Competition       2017 NESdev Competition       2016 NESdev Competition       2014 NESdev Competition       2011 NESdev Competition    Newbie Help Center    NES Hardware and Flash Equipment       Reproduction    NESdev International       FCdev       NESdev China       NESdev Middle East Other    General Stuff    Membler Industries    Other Retro Dev       SNESdev       GBDev    Test Forum Site Issues    phpBB Issues    Web Issues    nesdevWiki