Prev: Free PC Oscilloscope Software Preferences ?
Next: Are low/lower cost USB Oscilloscope's any good?
From: John Fields on 2 Dec 2006 06:59
On 1 Dec 2006 12:29:20 -0800, "jimi" <jim_fen05(a)yahoo.co.uk> wrote:

>Thanks for the replies, however, I asked the question so I could avoid
>using a microcontroller.

---
Is this application for a one-off, or are you planning on building a
quantity of these?


--
JF
From: John Fields on 2 Dec 2006 07:14
On 1 Dec 2006 22:06:01 -0800, bill.sloman(a)ieee.org wrote:

>
>John Fields wrote:
>> On 30 Nov 2006 13:24:39 -0800, "jimi" <jim_fen05(a)yahoo.co.uk> wrote:
>>
>> >Does anyone know of an alternative for the 74C925 chip for driving 4x7
>> >segment LED's. The chip seems to be obsolete. Thanks
>>
>> ---
>> http://www.1sourcecomponents.com/partinfo/74C925.htm
>>
>> http://www.intersil.com/cda/deviceinfo/0,1477,ICM7217,0.html
>
>So you wnat the OP to replace a 16-pin DIP with a 28-pin DIP that
>Intersil has marked "inactive".

---
1. I don't "want" the OP to do anything; I presented him with an
option to the 925 as he requested. Whether he chooses to use
it or not is entirely up to him.

2. Whether Intersil has marked it inactive or not, the part is
currently in production and is available. Digi-Key, for
example, has 807 pieces in stock, Newark-in-One 236, and I
suppose if took the time to look further I could find even
more sources.
---


>> A small microcontroller, however, would be my first choice.
>
>I'd prefer a programmable logic part - the 4-digit counter is not
>synchronous with the multiplexing logic for the display. Back in 1972 I
>dealt with this problem by freezing the multipexing clock until any
>incoming count had rippled through the (asynchronous) counters, which
>took up to 4usec. This wasn't an elegant solution.

---
Yes just the filament supply for all those 12AT7's must have been
unwieldy, to say the least.
---

>With a
>microcontroller, I guess you'd rely on the interrupt system to capture
>clock increments that occured at the wrong instant, and you'd keep your
>interrupt handler short and quick to keep the maximum count rate
>respectable.

---
Something like that...
---

>Programmable logic offers true parallel processing, which can be a lot
>tidier.

---
If needed.



--
JF
From: bill.sloman on 2 Dec 2006 08:03

John Fields wrote:
> On 1 Dec 2006 22:06:01 -0800, bill.sloman(a)ieee.org wrote:
>
> >
> >John Fields wrote:
> >> On 30 Nov 2006 13:24:39 -0800, "jimi" <jim_fen05(a)yahoo.co.uk> wrote:

<snip>

> Yes just the filament supply for all those 12AT7's must have been
> unwieldy, to say the least.
> ---

I don't know what you were doing in 1972 - the fact that you haven't
yet got past 555's does suggest that you aren't an early adopter - but
my toy used TTL logic and Beckman 7-segment fluorescent displays, with
a few transistors to handle the voltage swings.

And not a filament in sight (nor any hidden filaments either)

Looked quite neat.

--
Bill Sloman, Nijmegen (but in Sydney at the moment).

From: John Fields on 2 Dec 2006 09:42
On 2 Dec 2006 05:03:07 -0800, bill.sloman(a)ieee.org wrote:

>
>John Fields wrote:
>> On 1 Dec 2006 22:06:01 -0800, bill.sloman(a)ieee.org wrote:
>>
>> >
>> >John Fields wrote:
>> >> On 30 Nov 2006 13:24:39 -0800, "jimi" <jim_fen05(a)yahoo.co.uk> wrote:
>
><snip>
>
>> Yes just the filament supply for all those 12AT7's must have been
>> unwieldy, to say the least.
>> ---
>
>I don't know what you were doing in 1972 - the fact that you haven't
>yet got past 555's does suggest that you aren't an early adopter

---
I'd say that statement more nearly categorizes your position than
mine since I adopted them way back when they first came out. You,
on the other hand, have yet to use one (by your own admission) so
I'd say you're the one who's a little late getting on the bandwagon.
---


>- but
>my toy used TTL logic and Beckman 7-segment fluorescent displays, with
>a few transistors to handle the voltage swings.
>
>And not a filament in sight (nor any hidden filaments either)

---
Sorry, Charlie, but vacuum fluorescent displays _do_ have filaments.

Where do you think the electrons used to illuminate the phosphors
come from, otherwise?
---

>Looked quite neat.

---
Yeah, I'm sure. VFD's are most always pleasant to look at.


--
JF
From: Spehro Pefhany on 2 Dec 2006 10:38
On Sat, 02 Dec 2006 08:42:44 -0600, the renowned John Fields
<jfields(a)austininstruments.com> wrote:

>On 2 Dec 2006 05:03:07 -0800, bill.sloman(a)ieee.org wrote:
>
>>
>>John Fields wrote:
>>> On 1 Dec 2006 22:06:01 -0800, bill.sloman(a)ieee.org wrote:
>>>
>>> >
>>> >John Fields wrote:
>>> >> On 30 Nov 2006 13:24:39 -0800, "jimi" <jim_fen05(a)yahoo.co.uk> wrote:
>>
>><snip>
>>
>>> Yes just the filament supply for all those 12AT7's must have been
>>> unwieldy, to say the least.
>>> ---
>>
>>I don't know what you were doing in 1972 - the fact that you haven't
>>yet got past 555's does suggest that you aren't an early adopter
>
>---
>I'd say that statement more nearly categorizes your position than
>mine since I adopted them way back when they first came out. You,
>on the other hand, have yet to use one (by your own admission) so
>I'd say you're the one who's a little late getting on the bandwagon.
>---
>
>
>>- but
>>my toy used TTL logic and Beckman 7-segment fluorescent displays, with
>>a few transistors to handle the voltage swings.
>>
>>And not a filament in sight (nor any hidden filaments either)
>
>---
>Sorry, Charlie, but vacuum fluorescent displays _do_ have filaments.
>
>Where do you think the electrons used to illuminate the phosphors
>come from, otherwise?

The Beckman displays were flat panel plasma discharge displays, sort
of like Nixies but segmented and with the segments all in one plane.
You used to seem them on gas pumps until fairly recently as well as
some industrial instruments (Simpson had a fairly successful series of
instruments that used them). National semi made a biplar driver chip
DS8880 or something like that.. ah, here it is:
http://www.sphere.bc.ca/test/nixies/ds7880.pdf

>---
>
>>Looked quite neat.
>
>---
>Yeah, I'm sure. VFD's are most always pleasant to look at.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff(a)interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
First  |  Prev  |  Next  |  Last
Pages: 1 2 3 4 5
Prev: Free PC Oscilloscope Software Preferences ?
Next: Are low/lower cost USB Oscilloscope's any good?