Open Source Scanfail Unit (phase 1)

[Banthai]

Audrey said ...

Please don't hang me if some things are wrong about this circuit, it's just a concept for others. According to the title of this thread this is just phase 1

great circuit .... and it is good that we can look at so many options,

im not quite sure when phase 2 will start, if anyone wants to suggest when we have concluded this phase and the next phase begins please kick it off in a new phase2 thread

my idea for the next thread would be laying down a ultimate circuit that comprises of all the best bits of the cicuits presented in this thread

all the best .... Karl

[mixedgas]

Intresting aproach.

I found the folowing interesting text:

The simplest scanfail interlock derives the vector velocity as the sum of the squares of the and Y velocity signals, comparing this against a threshold voltage. When the vector velocity is below the thresehold the beam is shuttered.

I have now idea how to do this with electronic components.

Is that I have no idea, or I now have a idea?

Analog multipliers, either log antilog, or the Gilbert style do that, They are a little expensive, we are hoping to build a cost effective simple circuit using a single quad opamp, or a low cost TTL part, so certain low cost galvo makers will adopt it as a standard feature on their scanner amps, as audince scanning easily gets out of control in clubs these days. . Log Antilog is temperature sensitive and tricky to adjust/use in quanity. Good Gilbert cell multipliers are basically a sole source part from Analog devices.

I will be glad to post you a sum of squares circuit but if your in a low labor cost foreign country making things in bulk your looking at ~20$ in parts, VS about 2.00$ for my origional circuit to Bill Benner's Specs or about $3.50 for Audrey's excellent current offering. A ideal board would use all three methods plus some sort of "watchdog" circuit to make sure the board self tested ok. The more complex you make it, the more likely the board itself will fail, and thus the simpler, the better, which is why Audrey and I are proposing such simple circuits.

One of the basic goals is to get some safety for club patrons exposed to low cost DPSS by making a standard.
The next step up would be the more sophisticated hobbyist board.
We can do both.

I THINK PHASE 2 IS I breadboarded something and the results were......

ALSO WE NEED TO FIGGURE OUT Some basic standards on HOW TO TEST THESE THINGS, BEFORE PHASE ii?

And Audrey, I'm in no mood to hang you, I'm in pain from a malfunctioning adreanal gland, which causes alternate rage and depression plus high blood pressure, so PLEASE excuse any DISRESPECT. I am impressed by your skill as a engineer, not too many people do your level of circuit design in digital.

btw its hard to type at 3Am after a rough day in the university lab.

Steve Roberts

[Miss A.]

Hey, my design count 7 simple IC's. What can go wrong with them?
A average computer contains maybe 200 IC's and processors and never fail. Its the software that will crash

Be honest: most people here don't have a scanfail system at all !!
What can possibly go wrong with our circuits? It's better then nothing.

The scanfail that's Medialas is selling is the SafeGuardII :


As you can see it's loaded with a processor and some SMD chips and costs 180 euro's. If Medialas could made this simpler or cheaper they had made it, but they didn't because it's almost impossible I think.

But maybe there is some light at the horizon. Please see my circuit above.
The output 09 is now connected to the RESET input of the CD4017.
If you rewire this output to the ENABLE input, then the whole circuit is safe!
If there is someting wrong with the ADC converter, the latches or the 74LS684, the NE555 still gives too many clocks to the CD4017.
Then the output O9 wil become HIGH and will make the ENABLE input HIGH too. So, the CD4017 stops and the opto will shut the laser too.
Kind of a watchdog selftest.

(is it?)

[mixedgas]

you ready for me to build it?

Steve

[mixedgas]

you ready for me to build it?


BTW AD8003 is showing tripple 1 Ghz video opamp, gota better number?

Steve

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[Miss A.]

Oeps, must be the AD8803.
http://www.analog.com/en/prod/0,,AD8803,00.html


.

[mixedgas]

Oeps, must be the AD8803.
http://www.analog.com/en/prod/0,,AD8803,00.html


.

AD7819



Steve puts on CD of Daft Punk's "ONE MORE TIME"

still not a valid number, how about AD7819 from digikey.com or do you want a "flash" converter? Hint Hint, I order my parts from mouser.com, digikey.com or jameco.com

Steve

[Miss A.]

What ever Steve.
Just find the best ADC for this job.
As long it has 8 bit output.

[Miss A.]

Hi All,

Here the new circuit with Steve's AD7819 ADC and more:



And the board (80mmx100mm):




OK, it's not perfected yet. If here someone who can make a trail version of this?

[mccarrot]

Looks great!, wil this circuit also detect if the operator draw only one beam, or a very small circle?

I do have doubs by using ADC, as they are probbably hard to find at a normal radio shack.