![]() The WIKA pressure switch PSD-30 is available either with PNP or NPN switching output. In contrast, in North America, the country where the transistor was invented, relay outputs with potential-free contacts for AC 110 V loads are most widely used. In my experience, PNP switching outputs are used mainly in Europe, and NPN outputs almost exclusively in Asia. When a change in signal takes place by reaching a pressure value, the supply voltage (U+) is “switched on”, allowing current to flow from U+ through the load via the transistor and to GND. The load is connected to the switching output with U+ as the reference point. When a change in signal takes place by reaching a pressure value, the supply voltage (U+) is “switched through”, allowing current to flow from U+ through the transistor and through the load to GND. The load is connected to the switching output with GND as the reference point. This is why the load must be connected differently to the transistor outputs. In principle, both are bipolar transistors in which only the internal arrangement of the pn transitions differs. Here is a brief explanation how the two different outputs should be connected. Good luck to everyone trying this.Manufacturers of electronic pressure switches often offer both PNP and NPN switching outputs. MadeInJapan wrote:I originally posted this as a reply to someone inquiring about how difficult replacing your own PNP switch was and then realized that we don't have a write-up on this in our database, so I've copied my reply here as a fresh post. Let us know how it goes by adding your comments! Turn the key off, put the gear selector back in PARK and button it up. At the GM factory, they would put silicone in the terminals to prevent water from getting in. ![]() Curt also gives a tech tip about removing the neutral safety switch without breaking the harnesses plastic housing. Now move the sensor so that it is between your two marks (reverse lights should be on) and tighten down. Bowtied 3 Curt goes over the Neutral Safety Switch on a 4L60E transmission. Mark the location with a pencil where it goes on, then rotate more until the reverse lights go out, mark with a pencil. Put the car in reverse (car on, engine not running) and turn the large metal part of the PNP switch forward and backward until you can get the reverse lights to go on and off in both directions. If you're doing the alignment alone, put a mirror behind the car such that you can see the reverse lights go on and off from where you're working. Here is the write-up from Volvospeed regarding the PNP replacement that will help you step by step (minus the added notes that you'll find necessary for alignment without the tool that I make below): With a zero signal applied to the Base of the transistor it turns OFF acting like an open switch and zero collector current flows. Then the transistor operates as a single-pole single-throw (SPST) solid state switch. The PNP switch has to be aligned within 3mm of what it's suppose to be for it to work at all so if you get it in and it doesn't work, don't assume that the switch is bad.it's probably the alignment. For a PNP transistor, the Emitter potential must be positive with respect to the Base. Inductive Proximity Switch M18 PNP IP67 PNP, NO and NC contact Power supply between 6 and 36 VDC IP67, water resistant With built-in LED High accuracy. This is really not that hard though.much easier than trying to get an alignment tool. ![]() A bunch of stuff has to be moved out of the way and then once it's in place you have to "adjust" or as they call it, align it. The PNP switch replacement is a bit of a pain. I originally posted this as a reply to someone inquiring about how difficult replacing your own PNP switch was and then realized that we don't have a write-up on this in our database, so I've copied my reply here as a fresh post.
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