A theoretical idea

oracacle

Senior Member
OK, I have done some head scratching, I maybe able to have my cake and eat it - so to speak. It would require a ground up rebuild of the current unit basing the system around a 20x2 instead of a 28x2.

here is what I am thinking, I have not finished the entire thing, I will use the IVR and comparator for the normal sensors. There will be additional connector or 2 to connect the screens (not sure if I am going to put the amp circuit on the screens or in the box as yet). I was leaning towards using 4 AA batteries again with either a LDO or buck reg. however I may go the same route as the macro rail and use a battery from a remote control car (which will need regulation of some description), I already have the charger so make some sense.

please note the circuit attached is incomplete.
 

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oracacle

Senior Member
Sorry for the delay I have had some personal issues and then someone went and knocked me off my bike the other day, its all getting a bit chaotic here.

any how, I have assemble the gate circuit and a problem arose. the output LEDs are flashing in an astable manner, I have checked my circuit and all seems to be correct. I a currently presuming that I may have damaged the LM224 IC.

I am going to try and forge ahead with the rest of the project for a minute, I may fall back onto wire screen of some description which I think could be made with some fly tying wire (any here fish?). I am going to bread board the entire timing circuit and experiment with 2 pieces of wire as a starting point.
 

OLDmarty

Senior Member
Not sure if anyone suggested this, but why can't you use the sound of the gunshot (or 'crack' of the air-rifle) as the SOUND-trigger source, then use a (trial & error) delay after the sound trigger to fire the camera....no need to capture speeding projectiles then ;-)

You have all the gear there working from sound trigger already....

just my 2cents...
 

techElder

Well-known member
Read the whole thread. The OP defined the project so as to eliminate the "trial and error" methods.
 

oracacle

Senior Member
yes I could use trial and error, but then what's the point of having processors and cool thing that can do stuff that make life easier. you can use log tables to get the answer to a logarithm, or you could pick up a calculator and have the answer in a fraction of time.

on a side note, I haven't gotten much further with the hardware, it been hard to fit in around various thing with getting the insurance claim sorted. I did make a start on some code and quickly came to the conclusion that a 20x2 doesn't have the code space (it would if it had separate slots each being 4096 bytes big) to be both the chronograph and flash controller, so until I or someone else figures out how to implement hippys' timer on a 28x2 while keeping the comparator free the 2 systems will have to remain separate which no big ordeal.
 

oracacle

Senior Member
I am still having issues with the IR gates after some new LM224s arrived. its maybe a voltage stability issue but not really sure at this point - or maybe an issue being caused by the output stage not being connected to anything other than the mono-stable indicator causing issues. Anyhow I went back over the SR latch to make sure I was going to use the correct one. I tried variations of NAND based and NOR based with clock adders of each and found that the best combination which most flexibility is a NAND based latch or NOR clock adder.

I am waiting on some 0.21mm copper wire to arrive before I start work on the screens.
I have most of the circuit on a bread board with the exception of the input switches and LCD output. I have also found that a new program can not be downloaded while the serial in (clock line) is connected to the logic so a small switch will need to be installed to make life easier when updating code.

I have mode a fair modification to Hippys' code to make use of the FPU, there are still changes to be made, and a lot more to add before the system starts to function like the final product. For the time being the programme just measures the time and calculates the speed between a fixed distance of 0.04m - this in the final build may well be alter-able to allow for much higher velocities (I don't think it going to be an issue mind).

I am going to do some testing were by a 28x2 (Using an AXE091) hold what will be the gate line high and then drops each one to simulate the gates being passed. this should give a fairly good idea of how accurate the system will be with a known time between each event and the timer giving its result.

I will be hopefully ordering the display, switches and alike on the 20th - payday, money has been pretty all over the place this month due to events at the end of last month. its been a long 14 days.
 

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oracacle

Senior Member
I found an error in my timing code that took rather longer to resolve than I would have liked.

here is the code for simulating the screen with a 28x2, I ran it at the default 8mhz, I will have a look at 16mhz and see how it look

Code:
[color=Navy]#Terminal 9600[/color]
[color=Blue]pause [/color][color=Navy]2000[/color]
[color=Blue]sertxd ([/color][color=Navy]13[/color][color=Black],[/color][color=Navy]10[/color][color=Blue])[/color]
[color=Black]main:
      [/color][color=Blue]high b.6                      [/color][color=Green]'b.6 is set
      [/color][color=Blue]high b.5                      [/color][color=Green]'b,5 is reset
      'if pinb.7 = 1 then
            [/color][color=Blue]low b.6                 [/color][color=Green]'set first screen low
            [/color][color=Blue]pause [/color][color=Purple]b0
            [/color][color=Blue]low b.5                 [/color][color=Green]'set second screen low
            [/color][color=Blue]sertxd ([/color][color=Black]#[/color][color=Purple]b0[/color][color=Black],[/color][color=Navy]13[/color][color=Black],[/color][color=Navy]10[/color][color=Blue])
      [/color][color=Green]'end if
      [/color][color=Blue]pause [/color][color=Navy]750                     [/color][color=Green]'wait for numbers to be printed
      [/color][color=Blue]inc [/color][color=Purple]b0                        [/color][color=Green]'increase delay
      [/color][color=Blue]if [/color][color=Purple]b0 [/color][color=DarkCyan]= [/color][color=Navy]255 [/color][color=Blue]then              [/color][color=Green]'check for not overflowing
            [/color][color=Blue]end
      endif
      goto [/color][color=Black]main[/color]
I have also attached a PDF of the numbers. pause denotes the 28x2 pause @ 8mhz, time is the period elapsed as timed by the modified hippy timer, speed is the speed as calculated by the FPU and excel is speed calculated by excel.

Edit: Added numbers for the 28x2 screen simulator at both 8 and 16mhz.
 

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