Jump to content
Electronics-Lab.com Community
Sign in to follow this  
bonanz

frequency to voltage noise filtering

Recommended Posts

Hello all,

i want to display the speed of a model train, the optical sensors (link below) are placed around the track, and i am using the lm2907 to pick up a frequency off of them and change it to a voltage. then i was feeding that voltage into some cascaded LM3914 bargraph drivers to display the speed on 20 led's.

I got the freq input going and had the LED's rigged up before, but now when i try to integrate them the resulting display on the row of LED's is really noisy and there seems to be a huge burst of voltage at low speeds, like if the train is going slow, whenever it trips a sensor the voltage leaps and lights almost all 20 led's for a split second and then drops back down. Just overall the response of the LED's seems too sensitive to fluctuations in speed, when i measure the output votage with a DMM and fluctuate the speed, the output voltage seems to increase/decrease appropriately without any wild fluctuations.

So my question is how can i get the LED's to not be so sensitive it seems and read the voltage more like the voltmeter. Or can someone suggest another method to display the speed. Could i use a ICL7107 and a 3.5 digit display with a voltage divider to display the speed in like inches/sec or something. Would the ICL7107 have the same sensitivity problem? I guess i could probably also use an analog voltmeter and "redraw" the tick marks on the meter, but i'd like to have a nifty digital output of sorts. (note: i tried analog meter and similar results slightly better though, but still not good enough)

The max freq i anticipate is about 30Hz maybe 40. so i want to display speed from stop to about 30 Hz. here is a schematic of the circuit.
FTV-CIRC.JPG

sensors being used
http://www.optekinc.com/pdf/OPB620.pdf


Thanks
Bonanz

Share this post


Link to post
Share on other sites

:)hi bonanz,

would you care to provide me with the full circuit diagram of your project once you have solve this problem. i really would to help you out but am not very good at digitals, but am good in building circuits. :) i have read articles about those problem and what they suggest is to use pi filter.

hope this can solve your problem.

pls. email me once the problem is solve, thanx ;)

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

×
×
  • Create New...