| | | | |
 |  |  |  |
| |||||||
| Electronic Projects Design/Ideas/Reviews Are you building an electronic project or want to? Maybe you need some assistance? Come and submit your electronic questions here and let our experienced members find a solution. |
 |
| | LinkBack | Thread Tools | Display Modes |
13th May 2008, 10:29 AM
| (permalink) |
 I think i was over complicating it. So i use a non-inverting comparator which will give me a digital ouptut signal with the same polarity as the input signal. I then choose the correct feedback resistor to give which sets the limits. I change the vref by changing the value of reisitor? Thanks for your help | |
|
|
13th May 2008, 10:56 AM
| (permalink) | |
| Quote:
The blue text is correct. The Vref is usually set by two resistors forming a potential divider from the +Vsupply to the 0V. Its a good idea while you are testing, to add a variable resistor in series with two fixed resistors. Something like this drawing. REMEMBER: the LM324 OPA does not make a good comparator..
__________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/ Last edited by ericgibbs; 7th July 2008 at 12:24 PM. | ||
|
|
|
14th May 2008, 10:38 AM
| (permalink) |
| Does this look better i had a bit of problem using my first set-up. Does this look better to you? | |
|
|
|
14th May 2008, 12:04 PM
| (permalink) | |
| Quote:
I have changed the value of the resistors, they were too low. Also the 10K from Vref is not required, but I usually use a 470R. Why have you deleted the Rh hysteresis set pot,?? Otherwise looks OK. 
__________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/ Last edited by ericgibbs; 7th July 2008 at 12:25 PM. | ||
|
|
|
14th May 2008, 11:12 PM
| (permalink) |
| Is the hysteresis set pot just a varaiable resistor to help set it?? | |
|
|
|
15th May 2008, 08:15 AM
| (permalink) | |
| Quote:
Setting the required level of hysteresis and the upper/lower voltage limits using 'preferred values' of resistors can be tricky. Problem is, when you change the Rh [fixed] resistor the Vref point moves, so you adjust the Vref and then the switching limits change... I have found the easiest way is to calculate an approximate value of Rh and Vref, then include in the Vref and the upper/lower hysteresis circuit, variable resistors. The variable can be replaced for fixed resistors after you have determined the required fixed values. [you measure the resistance values of the variable resistors] Do you follow.?
__________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/ | ||
|
|
|
| Bookmarks |
| Thread Tools | |
| Display Modes | |
| |
Similar Threads | ||||
| Title | Starter | Forum | Replies | Latest |
| Help, Schmitt trigger | rngd | General Electronics Chat | 22 | 25th February 2008 05:10 PM |
| Need help with Schmitt trigger application! | whirlwindz | General Electronics Chat | 8 | 23rd May 2007 01:06 PM |
| PIC – RB0 Interrupt pin Schmitt Trigger input | elexhobby | Micro Controllers | 5 | 9th October 2005 10:31 AM |
| Calculating Schmitt Trigger | Wbdsgnr | General Electronics Chat | 1 | 29th March 2005 06:05 PM |
| diffferences between a TTL and a ST (Schmitt Trigger) I/O ?? | foosm | Micro Controllers | 2 | 27th August 2003 07:27 PM |
Linear Mode
