counting input from sensors

[Avital]

Hi,

I'm modifying a previous post of mine to form a different question:

I have an X (values may range from 1-128) amount of light sensors
whose output is fed to a 7414 - the result is a clean, ttl level "1"
or "0" in response to light/dark conditions on the sensor. I would
like to be able to count how many 1s I have using only ttl parts.

Thank you for your suggestions in advance.
Avital
ynospamavitalp@rogers.com

(remove the letter that sounds like "wye" and the words "nospam" to
get actual email)

 

[JeffM]

I would like to be able to count how many 1s I have using only ttl
parts.
Avital

Start here:
http://www.google.com/search?num=100&hl=en&lr=lang_en&ie=UTF-8&oe=UTF-8&safe=off&q=%22event+counter%22+g-knott&btnG=Google+Search

 

[Avital]

jeffm_@email.com (JeffM) wrote in message news:<f8b945bc.0311071728.1434c843@posting.google.com>...

I would like to be able to count how many 1s I have using only ttl
parts.
Avital

Start here:
http://www.google.com/search?num=100&hl=en&lr=lang_en&ie=UTF-8&oe=UTF-8&safe=off&q=%22event+counter%22+g-knott&btnG=Google+Search

My problem isn't as simple as counting the inputs one time - I should
have been more specific. I have 3 LED displays already setup to show a
count:

clock input->7490->7490->7490
| | |
7448 7448 7448
| | |
(*) (*) (*)

Where (*) represents a common-cathode 7-segment display. The chaining
of the 7490s isn't a rigid requirement, just the way things are setup
now.

I would like to show an accurate real time count of the number of
shaded sensors. That is, if the count is 5 at one point in time, but
2mins later is 3, I need to see that change. Counting up isn't a big
deal, but counting down, some sort of clever latching/display
reset/refresh rate solution, or some other logic is required.

Also, I require advice on power consumption issues regarding such a
large array of sensors. As 128 sensors would probably require a
relatively large number of ttl devices to interface to. Finally, I
would like opinions/advice on issues regarding the fact that these
sensors are spread out over a 1 meter surface in length - what power
issues/problems lie there, and how do I solve them? buffers?

So, as you can see, the starting point has already been passed
although, I did find the 8254 chip an interesting component that I may
use - but I'd rather exhaust the simplest ttl chip options first
though.

Thank you.
Avital

 

[Luhan Monat]

Avital wrote:

Hi,

I'm modifying a previous post of mine to form a different question:

I have an X (values may range from 1-128) amount of light sensors
whose output is fed to a 7414 - the result is a clean, ttl level "1"
or "0" in response to light/dark conditions on the sensor. I would
like to be able to count how many 1s I have using only ttl parts.

Thank you for your suggestions in advance.
Avital
ynospamavitalp@rogers.com

(remove the letter that sounds like "wye" and the words "nospam" to
get actual email)

Avital,

This much complexity is almost always handled with a microcontroller
today. Signals in, signals out, and software in the middle.

--
Luhan Monat, "LuhanKnows" At 'Yahoo' dot 'Com'
http://members.cox.net/berniekm
"The future is not what it used to be."

 

[John Fields]

On 8 Nov 2003 04:21:47 -0800, avip@hotmail.com (Avital) wrote:

My problem isn't as simple as counting the inputs one time - I should
have been more specific. I have 3 LED displays already setup to show a
count:

clock input->7490->7490->7490
| | |
7448 7448 7448
| | |
(*) (*) (*)

Where (*) represents a common-cathode 7-segment display. The chaining
of the 7490s isn't a rigid requirement, just the way things are setup
now.

I would like to show an accurate real time count of the number of
shaded sensors. That is, if the count is 5 at one point in time, but
2mins later is 3, I need to see that change. Counting up isn't a big
deal, but counting down, some sort of clever latching/display
reset/refresh rate solution, or some other logic is required.

---
Check alt.binaries.schematics.electronic in a little while for a
discrete CMOS solution.
---

Also, I require advice on power consumption issues regarding such a
large array of sensors. As 128 sensors would probably require a
relatively large number of ttl devices to interface to. Finally, I
would like opinions/advice on issues regarding the fact that these
sensors are spread out over a 1 meter surface in length - what power
issues/problems lie there, and how do I solve them? buffers?

---
Assuming 1mA max for each chip for the CMOS solution, you'll need 21
HC14's, 17 HC165's, 3 HC160's, 3 HC4511's, and 1 HC40103, for a total
of 45mA for the logic.

Power issues for your sensor array? Who knows? You haven't pasted
anything at all about that in terms of what your sensors are, how much
power they consume, what tour power supplies look like, etc...
---

So, as you can see, the starting point has already been passed
although, I did find the 8254 chip an interesting component that I may
use - but I'd rather exhaust the simplest ttl chip options first
though.
---

--
John Fields

 

[Avital]

John Fields <jfields@austininstruments.com> wrote in message news:<l1fqqv0prt715oe09k4l1mkemrooqtodt0@4ax.com>...

On 8 Nov 2003 04:21:47 -0800, avip@hotmail.com (Avital) wrote:


My problem isn't as simple as counting the inputs one time - I should
have been more specific. I have 3 LED displays already setup to show a
count:

clock input->7490->7490->7490
| | |
7448 7448 7448
| | |
(*) (*) (*)

Where (*) represents a common-cathode 7-segment display. The chaining
of the 7490s isn't a rigid requirement, just the way things are setup
now.

I would like to show an accurate real time count of the number of
shaded sensors. That is, if the count is 5 at one point in time, but
2mins later is 3, I need to see that change. Counting up isn't a big
deal, but counting down, some sort of clever latching/display
reset/refresh rate solution, or some other logic is required.

---
Check alt.binaries.schematics.electronic in a little while for a
discrete CMOS solution.
---

Also, I require advice on power consumption issues regarding such a
large array of sensors. As 128 sensors would probably require a
relatively large number of ttl devices to interface to. Finally, I
would like opinions/advice on issues regarding the fact that these
sensors are spread out over a 1 meter surface in length - what power
issues/problems lie there, and how do I solve them? buffers?

---
Assuming 1mA max for each chip for the CMOS solution, you'll need 21
HC14's, 17 HC165's, 3 HC160's, 3 HC4511's, and 1 HC40103, for a total
of 45mA for the logic.

Power issues for your sensor array? Who knows? You haven't pasted
anything at all about that in terms of what your sensors are, how much
power they consume, what tour power supplies look like, etc...
---

So, as you can see, the starting point has already been passed
although, I did find the 8254 chip an interesting component that I may
use - but I'd rather exhaust the simplest ttl chip options first
though.
---

John,

Thank you for posting a schematic, it was useful to see the ideas
being discussed in a diagram. After further consideration (I've
described another possible design in another post), I'm resolved to
the fact that there is no real clean plain-part ttl or cmos solution.
There are simply too many sensors.

In a last attempt to try to reduce the count, I have been toying with
the idea of an xy grid representation of sensors using schmitt
transceiver with tristate output. I haven't fully analysed whether or
not it will work but the gyst of the idea is this:

xy grid of sensor inputs whose row/cols are terminated by schmitt bus
transceivers. Transceivers are enabled via decoders in sequence, their
output is piped via mux or shift registers (with a seperate clock and
some logic) to an AND gate. So, sequentially, every strobed xy point's
output is sent to the AND gate (one from the x-row, one from the
y-col), which, in turn, is finally piped into the chained 7490s
controlling the count. Hope I've explained it clearly enough.

This design seems to cut the chip requirements by about half, however,
this is still not the most novel or extensible solution. I'm
considering CPLD solutions now. Any advice on this front would also be
much appreciated. At the moment I'm researching solutions from Xilinx
but not fully clear about what a beginner kit would be. It seems that
I should simply pick any CPLD that fits my current/future
pin/macrocell requirements, buy the demo board offered on the site,
use their free WebISP software, and use my VHDL book

When I asked about power requirements on the sensors, I should have
been more specific, I was prompting for more advice on pitfalls I
should expect rather than specific issues. My sensors are simple
photodiodes with a resistor, my choice for photodiodes was completely
controlled by their relatively-to CdS and Phototransistors-cheap
price. I was wondering what I should keep in mind when dealing with so
many sensors spread out over such a large surface - resistance in long
wires, capacitance issues, speed issues, mechanical considerations,
designs which lead to unrealistic power supply expectations, other
electrophysical problems, etc.

Thank you for your help and advice! (that goes for everyone who posted

Avital

 

[Robert Monsen]

"Avital" <avip@hotmail.com> wrote in message
news:6430a1f3.0311070200.4baa1417@posting.google.com...

Hi,

I'm modifying a previous post of mine to form a different question:

I have an X (values may range from 1-128) amount of light sensors
whose output is fed to a 7414 - the result is a clean, ttl level "1"
or "0" in response to light/dark conditions on the sensor. I would
like to be able to count how many 1s I have using only ttl parts.

It sounds like you are already abandoning the traditional logic route.

Given that, one option would be to build a little data bus based on tristate
latches, and walk through them one by one, adding the ones up with a
microprocessor. This is by far the cheapest solution, in my opinion. You
would need 16 tristate 8 bit latches (74F825, for example), a 4 to 16 demux
(like a 74F154), a micro with at least 19 I/O pins, and a tiny bit of
software. Thats 8 input bits for the data bus, 4 selector bits for the
'address bus' and another 7 output bits for the result.

The result would not be 'instantaneous', but you could cycle through the
sensors 1000 times per second with little trouble using a 4MHz uController.

Regards,
Bob Monsen

 

[John Fields]

On 9 Nov 2003 13:19:31 -0800, avip@hotmail.com (Avital) wrote:

Thank you for posting a schematic, it was useful to see the ideas
being discussed in a diagram. After further consideration (I've
described another possible design in another post), I'm resolved to
the fact that there is no real clean plain-part ttl or cmos solution.
There are simply too many sensors.

In a last attempt to try to reduce the count, I have been toying with
the idea of an xy grid representation of sensors using schmitt
transceiver with tristate output. I haven't fully analysed whether or
not it will work but the gyst of the idea is this:

xy grid of sensor inputs whose row/cols are terminated by schmitt bus
transceivers. Transceivers are enabled via decoders in sequence, their
output is piped via mux or shift registers (with a seperate clock and
some logic) to an AND gate. So, sequentially, every strobed xy point's
output is sent to the AND gate (one from the x-row, one from the
y-col), which, in turn, is finally piped into the chained 7490s
controlling the count. Hope I've explained it clearly enough.

---
If you wanted to assemble the sensors into an X-Y array you could set
them up as an 8 column (enables) X 16 row (outputs) array and you could
use sixteen HC7540's as the Schmitt triggers. Strobe the columns with an
HC138 and the rows with an HC4067 and your chip count for the array
shrinks to 18 for the array.
---

This design seems to cut the chip requirements by about half, however,
this is still not the most novel or extensible solution. I'm
considering CPLD solutions now. Any advice on this front would also be
much appreciated. At the moment I'm researching solutions from Xilinx
but not fully clear about what a beginner kit would be. It seems that
I should simply pick any CPLD that fits my current/future
pin/macrocell requirements, buy the demo board offered on the site,
use their free WebISP software, and use my VHDL book

---
Once you've gotten the array shrunk down so that it can be controlled by
seven logic lines it seems kind of silly to do the rest with discretes
when, with a simple micro and four shift registers, you can do
everything else including driving the LED arrays statically.
---

When I asked about power requirements on the sensors, I should have
been more specific, I was prompting for more advice on pitfalls I
should expect rather than specific issues. My sensors are simple
photodiodes with a resistor, my choice for photodiodes was completely
controlled by their relatively-to CdS and Phototransistors-cheap
price. I was wondering what I should keep in mind when dealing with so
many sensors spread out over such a large surface - resistance in long
wires, capacitance issues, speed issues, mechanical considerations,
designs which lead to unrealistic power supply expectations, other
electrophysical problems, etc.

---
Describe your array in more detail and I'm sure more detailed advice
will be forthcoming.

--
John Fields