Subject:
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Re: Polariod Sonar
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 28 Nov 1996 06:51:50 GMT
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Original-From:
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MAR ERICSON <mar@/SayNoToSpam/cooper.edu>
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Viewed:
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1505 times
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I think you're right.
I used a transistor to drive the INIT with its emmiter and feed the TTL signal to the base. It seems to work fine now. :)
You know what's funny, I tried using a CMOS chip (HCT) and it was able to drive the INIT signal. I figure since the Octal Latch of the HB is CMOS...
But...the CMOS chip seemed to have a 4.4 msec propagation delay. :( So, that's when I tried the transitor rig. And 4.4 msec translated to about 5 feet! So, I had to discard the CMOS chip. I got it from radio shack. I heard bad things about Tandy so could this be one of them?
> > I'm trying to use TTL output of 74 series IC's to signal to INIT. I can't get it to work properly. Here's the deal. When I touch INIT to the 5V bus, the transd
> > Looking closely at the TTL output, I found that it drops from 5.149 V to 3.58 V the moment I connect INIT to it. And apparently, it doesn't stay at 5 V long en
>
> Although I teach a digital electronics class based on the 74xx series, I'm certainly no
> expert, but here goes anyway...
>
> TTLs seem to have a very low ability to drive anything but minimal loads. Look up
> "drivers" in the TTL Data Book. They provide a better output for other devices. We use
> them for driving 7-segment LEDs. I suspect that your INIT is drawing too much current
> and loading down your 74xx. I'll keep tuned in to see what others can add.
> --
> Richard T. Vannoy II richardv@abac.com
> PO Box 103 Computer Programmer
> La Mesa, CA 91944-0103 College Electronics Instructor
>
>
>
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Message is in Reply To:
 | | Re: Polariod Sonar
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| (...) Although I teach a digital electronics class based on the 74xx series, I'm certainly no expert, but here goes anyway... TTLs seem to have a very low ability to drive anything but minimal loads. Look up "drivers" in the TTL Data Book. They (...) (28 years ago, 24-Nov-96, to lugnet.robotics.handyboard)
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