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Author Topic: formula for slotted disc  (Read 21340 times)

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Offline RICH

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Re: formula for slotted disc
« Reply #10 on: September 27, 2012, 06:44:35 AM »
It's been a long time since using a slotted disc and remember having similar problems and think i just increased the diameter of the disc and also made the slot wider (may be double the calculated ) as the calculated value was too slim. You can make the slot quite wide, so use the calculated as a quide to start with. When fooling around, I used disc's made from a CD which was painted black and just widened the slot until it would read 3450. You can also cut numerous slots and see the affect just by putting black tape over the slots not being used. The above is easy and cheap to do. Sorry I can't be more definitive.

Good point on the response time Hood. Before using the Halls sensor i used a read switch and after reading up on that switch  found that is would not be fast enough. 

RICH
Re: formula for slotted disc
« Reply #11 on: September 27, 2012, 09:15:40 AM »
Hood,
4 In Disk
.375 width slot

Rich,
I though about using a cd (Great Idea).
I will try widening the slot

Thanks
Re: formula for slotted disc
« Reply #12 on: September 27, 2012, 09:50:39 AM »
Rich,
I widened the slot about 50%, it still maxes out at 2340
Thanks though

Offline Hood

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Re: formula for slotted disc
« Reply #13 on: September 27, 2012, 09:55:29 AM »
I had about 100mm dia with 10mm slot on the BP and it worked fine. I used an OPB 917B for the opto but I am sure the PMDX one will be up to the job so maybe its something else.
Do you have any Index Debounce set, if you do put it to Zero.
Hood
Re: formula for slotted disc
« Reply #14 on: September 27, 2012, 10:01:19 AM »
Hood,
My index debounce was at 5, I changed it to 0.
It did not have an effect on the rpm reading

Offline Hood

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Re: formula for slotted disc
« Reply #15 on: September 27, 2012, 10:22:47 AM »
Are you puuting the signal in via a BOB with optos? Maybe the optos are too slow.
Hood
Re: formula for slotted disc
« Reply #16 on: September 27, 2012, 10:54:04 AM »
I am pretty sure it has optos
i will check manual
I am using a pmdx 122 bob

Offline Hood

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Re: formula for slotted disc
« Reply #17 on: September 27, 2012, 01:20:25 PM »
The 122 should be fine as thats what I used.
If you attach your xml I will have a look in case there is something in it that could be an issue, cant think what but you never know.
Hood
Re: formula for slotted disc
« Reply #18 on: September 27, 2012, 02:02:33 PM »
I got it hood, It was the pmdx 106 speedcontrol . I had the anaolog voltage set at 5 volts . It needed to be 10 volts for the vfd. Works great now
Thanks Again guys

Offline Hood

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Re: formula for slotted disc
« Reply #19 on: September 27, 2012, 03:29:42 PM »
Great :)
Hood