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???
05/05/06 17:09
Modified:
  05/05/06 17:19
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 		 #115699 - Suggestion
Responding to: ???'s previous message
Can you change the circuit, or can you only add something to the input?

Assuming that you can change it and refering to the upper circuit (the lower one will not work!), I recommend you the following:

1. Remove R2, connect the anode directly to +5V. Connect a 100nF/X7R cap from +5V to GND.

2. Move C1 behind R4, so that it touches the cathode of OPTO-LED.

3. Change the transzorb. You should use an unidirectional transzorb, for instance SMAJ5.0A, with its anode connected to GND.

4. Increase C1 drastically (up to 100µF max), to increase the time constant of your RC-low pass filter. Up to now corner frequency of your filter is 1/(2 x pi x 1k//1k x 1µ)sec = 318Hz, which helps not very much.

Kai

List of 66 messages in thread
TopicAuthorDate
High Tolerant Input Pins tvs, otpto,            01/01/70 00:00      
   Use a 'srial chip            01/01/70 00:00      
      But..            01/01/70 00:00      
         what's the problem?            01/01/70 00:00      
      Re: Serial Chip            01/01/70 00:00      
         better or not            01/01/70 00:00      
   Suggestion            01/01/70 00:00      
   Input            01/01/70 00:00      
      Why damaged?            01/01/70 00:00      
         Re: Why Damaged.            01/01/70 00:00      
            Another suggestion...            01/01/70 00:00      
               Yes, but...            01/01/70 00:00      
                  Schottky clamps ?            01/01/70 00:00      
                     Diode clamps            01/01/70 00:00      
                        Tranzorb            01/01/70 00:00      
      Try this...            01/01/70 00:00      
   ST overvoltage protection            01/01/70 00:00      
      A bad situation            01/01/70 00:00      
         Russell            01/01/70 00:00      
            My suggestion?            01/01/70 00:00      
   Look for PLC discrete input circuits            01/01/70 00:00      
      partially right            01/01/70 00:00      
         Even a PLC wouldn't like this circuit            01/01/70 00:00      
            OK, It's a switch - question to Scott            01/01/70 00:00      
               Speed of the input            01/01/70 00:00      
                  at lower detection rates ...            01/01/70 00:00      
                     What I recommended...            01/01/70 00:00      
   Steroids Desing            01/01/70 00:00      
      Analyse the circuit            01/01/70 00:00      
         to fully isolate            01/01/70 00:00      
            how about answering            01/01/70 00:00      
               That's obvious isn't it?            01/01/70 00:00      
                  it's not that obvious            01/01/70 00:00      
                     It's just ignorance            01/01/70 00:00      
                        opto couplers            01/01/70 00:00      
                           true enough!            01/01/70 00:00      
                           Not so strange            01/01/70 00:00      
                              Not strange, perhaps, but WRONG!            01/01/70 00:00      
                     It's just ignorance            01/01/70 00:00      
                     maybe you answered this one yourself            01/01/70 00:00      
                        still waiting            01/01/70 00:00      
                           No, though that might help            01/01/70 00:00      
   is this a newfangled idea            01/01/70 00:00      
      Downunder circuitry            01/01/70 00:00      
   Why I use the opto            01/01/70 00:00      
      Perception vs reality            01/01/70 00:00      
      +5V supply, is it isolated?            01/01/70 00:00      
         already asked and asked again            01/01/70 00:00      
            Yes, last try before I leave the thread!            01/01/70 00:00      
               The +5V is Isolated.            01/01/70 00:00      
                  incomplete answer            01/01/70 00:00      
                     Yes, what about the grounds?            01/01/70 00:00      
                        Scott, where are you?            01/01/70 00:00      
                           he left when we asked questions            01/01/70 00:00      
                              Still lost and confused            01/01/70 00:00      
                                 you do not need a scope to answer the qu            01/01/70 00:00      
                                 We cannot help you, if you do not...            01/01/70 00:00      
                                    COM and E-GND            01/01/70 00:00      
                                       still not answered            01/01/70 00:00      
                                          just a minute ...            01/01/70 00:00      
                                             SO let me rephrase: how many ohms betwee            01/01/70 00:00      
                                                Getting Older            01/01/70 00:00      
                                                   if you want help, start with some answer            01/01/70 00:00      
                                                   Problem is much more complex            01/01/70 00:00      
                                                   what do you mean by "dying"            01/01/70 00:00      
                                                      Scott, could you...            01/01/70 00:00      

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