Need help to recognize this device

Discussion in 'The Projects Forum' started by aya, Dec 1, 2006.

  1. aya

    Thread Starter Member

    Nov 30, 2006
    14
    0
    [​IMG]

    what is the m s b at the right?
    rookie question,but any help will be appreciated.
     
  2. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    If it were a Digital circuit, I might be tempted to say "Most Significant Bit (or Byte)"... but hard to tell with what you have given us. Looks like each letter relates to an individual line on a 3 pin connector... and each line looks like it is connected to a set of contacts on a relay...... the diagram you have posted is quite unclear.
    could be "Mad Systems Builder".....
     
  3. aya

    Thread Starter Member

    Nov 30, 2006
    14
    0
    [​IMG]

    from this diagram there seems to be a switch?
    and it's true it connect to a relay
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    It's anyone's guess. The illo is a snake's nest wiring diagram for hooking up building block components in an electronic trainer of some kind. If the block in question was a switch or relay, I'd expect to see "C" for common, "N/O" for normally open, and "N/C" for normally closed. The one schematic symbol on the block seems to be a coil, which supports the guess about a relay. No contacts are shown, though.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Wild guess: Switch, Made (making contact), and Broken (contact broken)

    What do I win if I'm right?:)
     
  6. Johann

    Senior Member

    Nov 27, 2006
    182
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    Hi! It definately looks like the contacts of a single pole change-over relay and may be connected to some external circuitry, eg. light, buzzer, alarm, BOMB! etc.
    The letters, according to your schematic diagram: S (SOURCE?) is the COMMON, B is the normally closed contact (probably B stands for BREAK) and M is the normally open contact (M for MAKE).
    Anyway, that's how I interpret it!
     
  7. Teg Veece

    Member

    Mar 14, 2005
    21
    0
    Yes, definitely a switch. When the PIC output pin is HIGH (H), there is an insufficent voltage drop across the base emitter junction of the transistor so the device is off and no current flows through it.
    When the PIC's output goes LOW (L), the transistor is turned on and it pulls a current from the 5 volt supply through the inductor which generates a magnetic field and closes the switch (i.e. makes a contact between S and M).
    The diode is there to protect the transistor when the PIC's output goes HIGH again by rerouting the residual current as the inductor converts its magnetic energy back into electrical energy.
     
  8. aya

    Thread Starter Member

    Nov 30, 2006
    14
    0
    take a look at the picture.the M S B is the black thing to the left of the rely.the led is to confirm that the circuit works.Because I'm trying to build that circuit ,so what I really need to know now is what is this MSB?Will the rely still work without it?
     
  9. aya

    Thread Starter Member

    Nov 30, 2006
    14
    0
    sry forgot the pic[​IMG]
    And to Teg Veece,do you mean the MSB is acting as a switch to the rely?

    To thingmaker3,maybe I could post some design so you could enjoyig build them:)
     
  10. Teg Veece

    Member

    Mar 14, 2005
    21
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    aya, It's a MSB is a relay. When RA3 on the PIC is HIGH, the whatever is connected to S is becomes connected to whatever is connected to B. When RA3 is LOW, whatever is connected to S becomes connected to whatever is connected to M.
    That's about all I can tell you based on the info you've given. Maybe if we knew what you were trying to build we could offer you some more help. Sometimes relays are included in circuits so the user can add more devices easily and the circuit should still work if even if you decide to leave it out. But if M and B have been connected to other points within the circuit by the manufacturer then it's probably crucial to the operation of the component.
     
  11. aya

    Thread Starter Member

    Nov 30, 2006
    14
    0
    this is the full design,could you tell what is the MSB doing from this diagram?and by the way,is it necessary to use a relay in this case?is there any alternatives? [​IMG]
     
  12. aya

    Thread Starter Member

    Nov 30, 2006
    14
    0
  13. Teg Veece

    Member

    Mar 14, 2005
    21
    0
    From that schematic, the MSB relay appears to be electrically sepearate from the rest of the circuit so you could remove it an the circuit would still work. What exactly is the circuit meant to do though?
     
  14. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Since the design uses a PIC microcontroller its purpose is not easily determined.

    One can however make a few observations about what it might be based on the Input/Output features in the design.

    There are 4 input signals. One is the start button which is sampled by the processor. The other is the stop button which is connected directly into the PIC. The remaining 2 inputs are a couple of digital switches. These switches provide an eight bit digital value that can be read by the PIC.

    The output consists of 3 PIC digital IO lines feeding a 3-lines to 1-of-8 line decoder. This is used to scan the start switch, the two 4-bit digital input switches and also to multiplex the four 7-segment displays.

    Each of the 7-segments of the four 7-segment displays are bussed together and connected to the 8-bit digital IO port of the PIC.

    My best guess would be a count-down timer of some sort. An 8-bit value is set using the 2 digital switches and this is loaded into the display. Upon pressing the start button, the PIC counts from the start value to 0 at which time it energizes the relay.

    hgmjr
     
  15. Johann

    Senior Member

    Nov 27, 2006
    182
    30
    I AGREE WITH TEG VEECE! Remove the relay if you don't want to use its contacts. I don't know much abouts PIC's, but I DO know that if any circuit has a relay with available contacts, then it is intended to be used to control something and THAT "something" depends on the purpose/application of/for the circuit.
    What are you supposed to do with your end result? That may just be the clue to the reason for the "mysterious" MSB. In other words, what is the output device to be controlled? As can be seen from your circuit, the relay seems to be an importand part of it and is even indicated by the on-off of the LED, but its contacts, M S B are not (presently) connected to anything. What is the aim of building this circuit? What is to be controlled?
    Let us know and I am sure your problem will be solved.
    Regards!
     
  16. aya

    Thread Starter Member

    Nov 30, 2006
    14
    0
    ya,hgmjr is right,the circuit is a count down timer.I was thinking of building a chess clock by using two of these timer.I'm thinking of using relay of one circuit to control the other timer.Do you think that will work?
     
  17. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    The relay contacts going to terminals MSB are probably to switch on some sort of visual or audible indicator when the countdown is complete.. (just a guess, as the exact function will be embedded in the PIC's programming)...
    I can see no reason to have the relay, or use to MSB contacts if that feature is not required.

    If the timer does indeed activate that relay after countdown, then of course it can be used to control another counter.
     
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