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SPTT reed relays

Discussion in 'General Electronics Discussion' started by Dannybaws, Apr 18, 2015.

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  1. Dannybaws

    Dannybaws

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    Apr 18, 2015
    Hi everyone.

    New here, not overly knowledgable about electronics but I've made a couple of things before.

    I am looking for some high quality magnetically shielded reed relays. The only problem is that most I'm finding are to replace two-way switches. i.e. SPDT. I need one with three positions i.e. Single Pole Triple Throw SPTT. Any advice on where I may find some of these or what search terms to use as googling SPTT reed relays has not given me very good results.

    Thanks

    Dannybaws
     
  2. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    There is no such thing as a "Single Pole Triple Throw SPTT" reed relay. Google reed relay construction and you will see why.

    If you need a three-position switch (ON-ON-ON) you will need at least two reed relays with two coils, or three reed relays with three coils, depending on how you want to actuate the switches and whether you are using SPST or SPDT reed switches. For example, three SPST NO (normally open) reed switches with three separate coils can be wired to implement a SP3T relay.

    What are you trying to do? Sketch a circuit and upload it here.
     
    shumifan50, davenn and ADRT like this.
  3. Dannybaws

    Dannybaws

    17
    1
    Apr 18, 2015
    Thanks for the info. After looking through some diagrams I understand how they work better now.

    The SP3T NO option makes sense to me. I'm away at work at the moment but in a couple of weeks when I'm home I'll have a look at the circuit board and get back to you. It's a 3-way switch from a guitar pedal I'm looking to modify. I'm thinking though that if I had 3 seperate SPST relays, I'd have to make sure that I don't accidentally close two of the circuits at once as the chipboard may not be designed to handle this.

    Thanks for the help :D
     
  4. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    If you have to make sure there is only one path active at any given time, then a pair of SPDT reed relays will do that. The signal is applied to the common (movable) contact of relay 1 and from there is appears at its N.C. contact (Output A) when relay 1 is de-energized.. The signal appears at the N.O. contact of relay 1 when it is actuated, and from there it connects to the common contact of relay 2, appearing on the N.C. contact (Output B) when relay 2 is de-energized. Actuating the coil of relay 2 with relay 1 still actuated will then transfer the signal to the N.O. contact (Output C) of relay 2. Note that when relay 1 is de-energized it does not matter whether relay 2 is energized or not, the signal will always appear on Output A.

    With both relays de-energized, you have Output A signal on the N.C, contacts of relay 1. If you want this output, as well as Output B and Output C, to be disconnected when both relays are de-energized the circuit becomes more complicated and more reed switches will be needed.
     
  5. Dannybaws

    Dannybaws

    17
    1
    Apr 18, 2015
    Thanks very much for the clear explanation, had to read it through a couple of times, but makes perfect sense. Cheers for taking the time :D

    Dan
     
  6. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    It's been awhile since I have had teenagers in my house, but at one time four of them were practicing as a rock band in my garage. There were a lot of strange effects boxes out there, but I don't remember the details, just the fact that they were LOUD! I think some of the effects pedals were "stab" pedals that somehow switched from one effect to another each time the pedal was pressed (or stabbed). This was probably a mechanical arrangement of the pedal switch, but I don't know for sure. Such an action could certainly be implemented electronically with reed relays, but it would require some tinkering.

    If you want to replace a single SP3T guitar pedal "stab" switch with reed relay switches, you may want to have just two SPST pedal switches, a left pedal and a right pedal, to operate the reed relays. If no pedal switch is pressed you get normal guitar feed to channel A. Press the left pedal to energize relay 1 and the guitar feeds to effects channel B or C, depending on whether the right pedal is pressed or not. Press the right pedal to energize relay 2 and the guitar feeds to effects channel C, provided the left pedal is still pressed.

    You can purchase alternating-action push-button switches for one or both pedals, so pressing and releasing the left pedal causes it to remain closed, enabling the player to choose effects channel B or C with the right pedal. Pressing and releasing the left pedal again would restore normal feed to channel A without effects. Using an alternating-action switch for the right pedal would allow the player to "pre-select" which effects channel (B or C) would be active when the left pedal was pressed.

    It is difficult to achieve a reliable alternating-action switch with simple reed relays. It requires a "memory" circuit to store the current state of the switch and a reliable way to "reset" the "memory" when the switch is actuated again. A trivial problem to implement mechanically, but not so much electronically with the good reliability necessary for a performance environment. No musician I know of wants to have to farkle around with controls and pedals trying to obtain the "effect" they need prior to fingering a complicated riff.

    So, what exactly are you trying to do? There may be some experienced guitar players here in the forum who can help. (I am not an experienced guitar player.)
     
  7. Dannybaws

    Dannybaws

    17
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    Apr 18, 2015
    Hi there. That all sounds quite interesting and I'll definetly keep that in mind in case I come across a situation like that, but it is slightly different from my setup and your previous post covers me I think. It's actually a 3-way toggle switch. As in a hand switch that has positions up, middle, down and I have no need to control with feet, only digitally. I'm using the guitar pedal only as a prototype and it's not really for guitar playing :D

    I can't say exactly what I'm doing at the moment. sorry to be mistereous!
     
  8. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Well, okay then. BTW, there is a special miniature toggle switch available that implements a SP3T switch action. No reed relays necessary if you operate this switch with your fingers, i.e., digitally.:D
     
  9. Dannybaws

    Dannybaws

    17
    1
    Apr 18, 2015
    touché
    :D
     
  10. davenn

    davenn Moderator

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    Sep 5, 2009
    ohhh good grief ... another of these threads :rolleyes::rolleyes:

    if you don't want to help us help you then there isn't much point keeping the thread open

    none of us are interested in playing the guessing game
     
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