Logic probe/pulser???

Discussion in 'General Electronics Chat' started by groovejet, Jan 22, 2011.

  1. groovejet

    Thread Starter New Member

    Jan 1, 2011
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    Hi there?

    I've bought a Logic Probe/Pulser in one unit, but as im just starting out at electronics, i dont know how to use the <snip> thing!

    It's no good just telling me that High is '1' and Low is '0' as i need a blow 4 blow account of how to actually use it. Basicly like your explaining something to a kid for the first time!!!! Then im still not guaranteed to understand !!!!!! That sort of in depth info!!!!!! lol:D:eek::confused:

    *Its a 72-500 Tenma from CPC catalogue
    *Max input signal 50MHz
    *Switchable between 0.5 and 400Hz
    *Input impedance 120KΩ
    What are the 3 little terminals on the probe? under each it says -PULSE----SQ-----EXT SYNC.? also yellow led with PULSE written above.

    Included is also a lead with a croc. clip and terminal on other end?

    Help will be most appreciated:D View attachment 26794
     
    Last edited by a moderator: Jan 23, 2011
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    You will have 3 connections.

    The probe itself, a red or positive clip lead and a black or negative clip lead.
    Clip the black to the ground of the circuit under test and the positive lead to the supply of the circuit under test. Only clip it to the supply of a digital circuit. Check your manual and be sure you are not exceeding the voltage of the probe.



    Touch the probe to the pin you want to test. A (usually) red light denotes a low, a (usually) green light denotes a high. No light means high impedance or no connection.


    Check the Digital lessons at the top of this forum, if you need to know the meaning of high and low.
     
    Last edited by a moderator: Jan 23, 2011
  3. eblc1388

    Senior Member

    Nov 28, 2008
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    The probe you have got is the same I have got many years ago, which I still use regularly, albeit in my case the logic probe & pulser are two separate units.

    High and Low level definition on the probe depends on type of IC circuits and supply voltages so there is no one single answer.

    On the probe there will be a switch(TTL/CMOS) to tell probe what type of circuit you are testing on.

    To use the probe, connects the probe to the supply of the logic circuit to be tested. This is required so that the probe can know what input voltage level is High/Low. So if you are using a 7805 regulator to power your IC circuit from a 9V source, the logic probe supply should be connected to the +5V rail.

    Red LED is Logic High and green LED is Logic Low.

    The TTL switch option should only be selected if you are working on TTL chips at 5V, otherwise leave it set to CMOS.

    The pulser enable user to "forcefully" override the logic input to the chip to mimic a level change, even with the input pin connected to an output pin somewhere. It does that by generating a very short pulse of opposite polarity, thereby not damaging the output stage of another chip.

    Anyway, the probe will be your best tool for many good years to come. Mine does.
     
  4. groovejet

    Thread Starter New Member

    Jan 1, 2011
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    Quote:
    What are the 3 little terminals on the probe? under each it says -PULSE----SQ-----EXT SYNC.? also yellow led with PULSE written above.?

    Thanx guys 4 your help..........Wrote 4 a lay man 2 understand
     
  5. groovejet

    Thread Starter New Member

    Jan 1, 2011
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  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Pulse puts a signal on the line, high or low.

    Pulse Square puts a squarewave on the line, at the selected frequency.

    Ext. Trigger is to connect to the trigger input of your oscilloscope so it can display what is happening at an output at the exact time you are pulsing the logic input.
     
  7. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
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    I'm sorry. Your combined logic probe+pulser does not have a "TTL/CMOS" switch so may be the probe knows how to distinguish that.

    The following image shows you more information on how to use the three pins.

    Normally, you use only the third pin(count from nearest end) to force a logic level change on an logic gate input.

    The probe will send out a pair of very short pulses, with one at logic high and one at logic low. One of these pulses will match the existing pin logic level so will cause nothing to change. The one with opposite polarity will "forcefully" changed the existing logic voltage level(for a very short time) to mimic a signal. If the chip is healthy, this brief change will be pick up and caused subsequent chip/gate output changes.

    The SQ and Sync pin is used for connection to other instrument. The SQ pin can be used also as a clock signal for gate input pin which is not driven by another pin. Its driving capability is limited.

    [​IMG]
     
  8. groovejet

    Thread Starter New Member

    Jan 1, 2011
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    Sorry L.Chung, could you please attach the image again as it didnt appear to be on your post?
     
  9. groovejet

    Thread Starter New Member

    Jan 1, 2011
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    Also, is there anything i should NOT do when im practicing with my Logic Probe/Pulser?
    For example, can the pulser force a signal that could damage any IC??
     
  10. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
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    Can any member confirm the image is displayed properly? It could be the problem of the browser on your side displaying .png image, groovejet?

    Don't worry too much. Using the instrument is pretty safe on every circuit I have tested in the past.

    The pulser will not damage any common logic IC such as TTL or CMOS.

    In real life, nearly 99% of the time you will be using the probe instead of the pulser.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    I can see it. Perhaps groovejet needs to clear out their browser's cache and cookies; that frequently helps to clear up such problems.
     
  12. groovejet

    Thread Starter New Member

    Jan 1, 2011
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    I just cleared out my cookies and when i returned to AAC i could see the image, but when i signed back in it had disappeared? SpOOkey!!!

    Help Please?
     
  13. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Perhaps you have too many programs running for the amount of memory and/or disk space on your computer?

    Is your browser's cache set for too much storage? 10MB to 20MB is usually about right. If it's set really large, you can have problems; same thing if it's too small.
     
  14. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,887
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    Groovjet,


    Are you going through a proxy server? I had similar problems with images on this website at work where we have a proxy server.
     
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