Need help identifying a switch.
October 20, 2005 9:04 AM Subscribe
Help me identify this switch [1 page pdf].
I am trying to wire a remote firing switch for this old calorimeter. The unit is from Parr and its model is a 1241; you can find the data sheet and circuit diagram here on Page 25 of the PDF. The switch is in the lower right hand cornor ("Ignition SW5"). I shouldn't have slept through my electronics classes (heh).
I need to identify what the 4 leads of that switch do so I can adapt it to a computer controlled system. Pushing the switch down i found that two of the terminals went to a closed circuit, so I figured all the switch was doing was connecting those two terminals. Wired it and sparked two wires together made the fuse blow. So there must be an op-amp or something that is mimicking a closed circuit but is really doing something else.
If I had a name for this switch I could probably look up more information on it. All that Parr sent me was that PDF with a picture of a switch.
Please help!
(Oh, and, an "Engineering" category would be helpful).
I am trying to wire a remote firing switch for this old calorimeter. The unit is from Parr and its model is a 1241; you can find the data sheet and circuit diagram here on Page 25 of the PDF. The switch is in the lower right hand cornor ("Ignition SW5"). I shouldn't have slept through my electronics classes (heh).
I need to identify what the 4 leads of that switch do so I can adapt it to a computer controlled system. Pushing the switch down i found that two of the terminals went to a closed circuit, so I figured all the switch was doing was connecting those two terminals. Wired it and sparked two wires together made the fuse blow. So there must be an op-amp or something that is mimicking a closed circuit but is really doing something else.
If I had a name for this switch I could probably look up more information on it. All that Parr sent me was that PDF with a picture of a switch.
Please help!
(Oh, and, an "Engineering" category would be helpful).
Considering the purpose for this switch, it *may* have a piezo crystal inside to generate a spark to set off model rockets or potato guns... am I at all right for the purpose? :-)
If it's got a piezo crystal inside then use a BBQ ignitor button.
Otherwise, without where the wires *GO TO* nobody will be of much help I'm afraid. The diagram doesn't even mention if it's a normally open or closed switch, or if it is momentary or not.
posted by shepd at 9:23 AM on October 20, 2005
If it's got a piezo crystal inside then use a BBQ ignitor button.
Otherwise, without where the wires *GO TO* nobody will be of much help I'm afraid. The diagram doesn't even mention if it's a normally open or closed switch, or if it is momentary or not.
posted by shepd at 9:23 AM on October 20, 2005
Looks like a regular old switch, momentary DPST. That means Double Pole, Single Throw. The Wikipedia entry for 'switch' might be useful. It just connects wires pairwise as long as the button is down, and the pairs are usually wires sticking out on opposite ends (black and black-white stripes would be one pair in your case). The schematic is a bit confusing, since one of the pairs appears to be shorted anyway. I can't say this from the schematic, but it's possible that both pairs have to be connected simultaneously, as the switch would do.
posted by springload at 9:33 AM on October 20, 2005
posted by springload at 9:33 AM on October 20, 2005
Response by poster: The switch on this on the unit looks a lot like the ignition switch for the remote firing unit. I'm pretty sure it is exactly the same. Don't really want to disconnect all the wires that are attached to the current switch, however, because they are soldered on but I may have to.
The witch causes two electrodes to fire a 24 volt peak to peak (AC) signal according to my multimeter. The leads are to be hooked up to some ignition wire that causes a sample of material to go boom in an oxygen enriched environment.
posted by nickerbocker at 9:47 AM on October 20, 2005
The witch causes two electrodes to fire a 24 volt peak to peak (AC) signal according to my multimeter. The leads are to be hooked up to some ignition wire that causes a sample of material to go boom in an oxygen enriched environment.
posted by nickerbocker at 9:47 AM on October 20, 2005
Best answer: Yup, I agree with springload. From looking at the circuit diagram, it looks like all you want is a normally-open switch connected across those two terminals. The other two terminals are apparently unused, but still connected to the power line.
Are you sure you shorted the right two wires when you did that test? Going from the diagram, you want to short the bottom two contacts of SW5 together. The other half of the power supply is going to the top two contacts. If you short one of the top contacts to one of the bottom contacts, you'll short out the power supply and blow a fuse (at best). Keep in mind that all those transformer windings (T1 through T4) will look more or less like a short at DC, so using an ohmmeter to see what's connected to what inside the calorimeter can be misleading.
But according to that drawing, the 'remote fire' switch works just by connecting those two contacts, which ends up applying power to the ignition leads via T4. Relay 4 does the same thing, but since I don't know much about calorimeters I don't know what relay 4 is for.
For computer control, you probably want a relay with SPST or DPST contacts, which you'd wire up and plug into the "remote fire" connector. (I for one welcome our new computer-activated calorimeter overlords, etc.) Figuring out what the relay needs to be rated to carry is the next trick. I'd suggest checking the rating on the fuse and exceeding it by a factor of 50-100%. Also, be careful of the computer possibly firing the thing when somebody's mucking with it.
posted by hattifattener at 1:39 PM on October 20, 2005
Are you sure you shorted the right two wires when you did that test? Going from the diagram, you want to short the bottom two contacts of SW5 together. The other half of the power supply is going to the top two contacts. If you short one of the top contacts to one of the bottom contacts, you'll short out the power supply and blow a fuse (at best). Keep in mind that all those transformer windings (T1 through T4) will look more or less like a short at DC, so using an ohmmeter to see what's connected to what inside the calorimeter can be misleading.
But according to that drawing, the 'remote fire' switch works just by connecting those two contacts, which ends up applying power to the ignition leads via T4. Relay 4 does the same thing, but since I don't know much about calorimeters I don't know what relay 4 is for.
For computer control, you probably want a relay with SPST or DPST contacts, which you'd wire up and plug into the "remote fire" connector. (I for one welcome our new computer-activated calorimeter overlords, etc.) Figuring out what the relay needs to be rated to carry is the next trick. I'd suggest checking the rating on the fuse and exceeding it by a factor of 50-100%. Also, be careful of the computer possibly firing the thing when somebody's mucking with it.
posted by hattifattener at 1:39 PM on October 20, 2005
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Are there any distinctive markings on the small switch element itself?
Barring that, I'd cut the leads on the switch, take an ohmmeter to each combination of two wires, and test each both pressed and unpressed. Make a little matrix of what's going on.
posted by trevyn at 9:12 AM on October 20, 2005