Re: [funwithtransistors] NPN or PNP proximity sensor?


Dec 24 10:13 PM

 


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#1134 Dec 24 10:13 PM

I have 5 3 wire proximity sensors, and no idea weather they are

NPN or PNP..... Anybody have any experience with these? All I know

is that they are one or the other, operate on 12V to 24V, and carry

100MA max current. There is a drawing that shows the switch being

between leads 1 and 2 or 2 and 3, and likewise what appears to be a

resistor (just a rectangle) labeled Rm across between the two leads that

are not switched. Lead 1 is always positive, and it appears that lead 3

is probably negative. Resistor value is not shown.



Anybody have any ideas? I would like to use these to replace

mechanical switches that are failing on the electro/hydraulic rear wheel

steering system I built for my forklift. It operates in 3 modes the way

I have it set up. In one mode it holds the rear axle straight

actively. In another mode the rear steers opposite the front which

considering the massive size of the machine is the mode I most often use

as the turn radius is very short, and in mode 3 you can steer the rear

with a lever so you can crab steer (move sideways at an angle). The

original mechanical / hydraulic 3 mode steering was nothing but

trouble. In mode 3 it would crab proportionally (which I seldom used).



If I can make these sensors work, I will probably use mosfets with

them so they carry no current at all, and the mosfets will operate the

solenoid valve.





Howard



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#1135 Dec 24 9:29 PM

All the 3 lead SS switches I've encountered were NPN open collector. Some have a weak pullup resistor, high value, with the intention that an external load like a relay, contactor or solonoid would provide the bulk of the pullup current, the 100mA for exampl would most likely be the sinking current rating of the OC-NPN switch. Somehow you'll have to figure out which of the 3 leads are Pwr, Out and Gnd.

Denis.

--- In funwithtransistors@yahoogroups.com, StoneTool owly@...> wrote:

>

> I have 5 3 wire proximity sensors, and no idea weather they are

> NPN or PNP..... Anybody have any experience with these? All I know

> is that they are one or the other, operate on 12V to 24V, and carry

> 100MA max current. There is a drawing that shows the switch being

> between leads 1 and 2 or 2 and 3, and likewise what appears to be a

> resistor (just a rectangle) labeled Rm across between the two leads that

> are not switched. Lead 1 is always positive, and it appears that lead 3

> is probably negative. Resistor value is not shown.

>

> Anybody have any ideas? I would like to use these to replace

> mechanical switches that are failing on the electro/hydraulic rear wheel

> steering system I built for my forklift. It operates in 3 modes the way

> I have it set up. In one mode it holds the rear axle straight

> actively. In another mode the rear steers opposite the front which

> considering the massive size of the machine is the mode I most often use

> as the turn radius is very short, and in mode 3 you can steer the rear

> with a lever so you can crab steer (move sideways at an angle). The

> original mechanical / hydraulic 3 mode steering was nothing but

> trouble. In mode 3 it would crab proportionally (which I seldom used).

>

> If I can make these sensors work, I will probably use mosfets with

> them so they carry no current at all, and the mosfets will operate the

> solenoid valve.

>

>

> Howard

>



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#1136 Dec 24 10:40 PM

I withdraw the question ;-) ..........................



I decided that I couldn't hurt the darn things, and hooked up leads

one and 3 to 12V+ & 12V- respectively on my breadboard, and connected my

double led "test light" (one each polarity) between #2 and the positive

rail. The light came on and when I passed my side cutters close to the

sensor, it went out. Swapped my polarity and the light went out until I

passed the side cutters close and it snapped on bright.



That makes it an NPN in my book................



These things are great!! All I have to do is connect to the gate on an

N channel mosfet and ground my solenoid valve through the mosfet.

Originally I had planned to replace my mechanical switches and connect

them to the solenoid valves through relays. This is simple and

elegant! I love these solderless breadboards!! Instead of

wondering, I simply plug a few things in and test. How did I ever

live without one for so long?





Howard



On 12/24/2012 03:13 PM, StoneTool wrote:

> I have 5 3 wire proximity sensors, and no idea weather they are

> NPN or PNP..... Anybody have any experience with these? All I know

> is that they are one or the other, operate on 12V to 24V, and carry

> 100MA max current. There is a drawing that shows the switch being

> between leads 1 and 2 or 2 and 3, and likewise what appears to be a

> resistor (just a rectangle) labeled Rm across between the two leads that

> are not switched. Lead 1 is always positive, and it appears that lead 3

> is probably negative. Resistor value is not shown.

>

> Anybody have any ideas? I would like to use these to replace

> mechanical switches that are failing on the electro/hydraulic rear wheel

> steering system I built for my forklift. It operates in 3 modes the way

> I have it set up. In one mode it holds the rear axle straight

> actively. In another mode the rear steers opposite the front which

> considering the massive size of the machine is the mode I most often use

> as the turn radius is very short, and in mode 3 you can steer the rear

> with a lever so you can crab steer (move sideways at an angle). The

> original mechanical / hydraulic 3 mode steering was nothing but

> trouble. In mode 3 it would crab proportionally (which I seldom used).

>

> If I can make these sensors work, I will probably use mosfets with

> them so they carry no current at all, and the mosfets will operate the

> solenoid valve.

>

>

> Howard

>

>

---------------

>

> Always keep electrons and holes flowing in opposite directions.Yahoo! Groups Links

>

>

>

>







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#1138 Dec 24 10:23 PM

Howard, ��Proximity sensors may be capacitive, photoelectric, magnetic or electro-magnetic and they come in various sizes, shapes and flavors.�� More information is needed.�� It might help if you posted a picture of the device or provide a more complete description.�� Is there any part number or other id on the device?�� ��Please forgive my directness, but why would you want to use an unidentified device with unknown specs in such a critical application?�� I am sure that you are well aware that fork-lifts are dangerous beasts, and�� I cannot imagine wanting to trust the steering of same to some unknown component.�� In this instance you may want to consider purchasing sensors with known specifications so you can design and build something that is reliable and perhaps a bit more safe. �� ��Jerry F. ��From: funwithtransistors@yahoogroups.com [mailto:funwithtransistors@yahoogroups.com] On Behalf Of StoneToolSent: Monday, December 24, 2012 2:13 PMTo: funwithtransistors@yahoogroups.comSubject: [funwithtransistors] NPN or PNP proximity sensor?



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#1139 Dec 24 11:55 PM

Jerry:

������ They are inductive............ and I've some info at least onthem.�� I know their current capacity, their operating voltage, andthe distance they are good for.���� What I wasn't sure of was the waythey should be hooked up.�� It turned out to be fairly simple.



������ You greatly overestimate the risks involved.���� I have mechanicallimit switches on it now and they are not reliable.���� This issecondary steering.... rear axle only, and I do not operate it atspeeds where there is really any danger.�� Top speed, used ONLY forroading is about 25 mph, and I use front steering at that speed.�� Anorbital system.�� (pure hydraulic).���� This is a HUGE lumbering beastthat weighs 28000 lbs, and I don't do anything fast with it.�� It hasextremely good brakes also.���� It's not the kind of forklift you areused to seeing roaring around in warehouses.���� It has tires that aretaller than I am, is designed to pick up very heavy loads.�� Up to12000 lbs, and is designed for outdoor use.���� Also I am the only onewho ever operates it, and I don't operate it in proximity to peopleor vehicles except very slowly.

������ Sensor failure only means that the rear stops steering.�� I flipa switch on the dash and the rear centers up and I use front onlysteering.���� It's the sort of machine you use in a log yard ofsawmill or something of the sort.���� Roughly the same size as thearticulated bucket loaders you see the state use to load sand ondump trucks and such.���� I have one of those too..........�� A 3 yardbeast of roughly the same size and weight.������ I like BIG toys ;-)����The rear steering on this machine was never reliable until I builtthe electro hydraulic system for the rear....... and then only untilone of the mechanical limit switches went on the fritz.�� It willwork fine for half an hour, and then all of a sudden the rear isn'tfollowing anymore.����



������ I've worked around the young lunatics on forklifts in warehousesbefore.......I understand your concern.�� It simply is misplacedhere.���� This is an awesome solution, one that should prove extremelyreliable.

������

������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������������ ������ ������ ������ ������ Howard



On 12/24/2012 03:23 PM, Gerald Feldman wrote:Howard, ��Proximitysensors may be capacitive, photoelectric, magnetic orelectro-magnetic and they come in various sizes, shapes andflavors.�� More information is needed.�� It might help if youposted a picture of the device or provide a more completedescription.�� Is there any part number or other id on thedevice?�� ��Pleaseforgive my directness, but why would you want to use anunidentified device with unknown specs in such a criticalapplicati on?�� I am sure that you are well aware thatfork-lifts are dangerous beasts, and�� I cannot imaginewanting to trust the steering of same to some unknowncomponent.�� In this instance you may want to considerpurchasing sensors with known specifications so you candesign and build something that is reliable and perhaps abit more safe. �� ��JerryF. ��From:funwithtransistors@yahoogroup s.com[mailto:funwithtransistors@yahoogroups.com] OnBehalf Of StoneTool

Sent: Monday, December 24, 2012 2:13 PM

To: funwithtransistors@yahoogroups.com

Subject: [funwithtransistors] NPN or PNPproximity sensor?



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#1140 Dec 24 11:32 PM

Thanks, Howard.�� I am reassured.�� After 39 years of working in a hospital, I just didn���t want to see anyone hurt.�� ��Jerry F. ��From: funwithtransistors@yahoogroups.com [mailto:funwithtransistors@yahoogroups.com] On Behalf Of StoneToolSent: Monday, December 24, 2012 3:55 PMTo: funwithtransistors@yahoogroups.comSubject: Re: [funwithtransistors] NPN or PNP proximity sensor?



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#1141 Dec 25 12:55 AM

Jerry:

������ I have worked on and with heavy equipment for 30+ years otherthan a few minor incidents involving stitches (on myself) never hadany kind of accident to speak of.������ I normally work alone largelyfor that reason.���� The most dangerous piece of equipment I own asidefrom a chainsaw (unless you include guns), is a hydraulic knuckleboom.�� A crane that picks 6000 pounds and bends in the middle asopposed to the type with a cable.�� It's truck mounted and swings 360degrees.�� The control console is at the base of the boom and I worryall the time when I have the outer boom in an extended (upward)position, about the potential of a load swinging back to me if thehydraulic were to fail.���� If the inner boom blew a hose, the loadwould simply go down. If the outer boom failed the load would godown and toward the truck.���� For that reason I work on the oppositeside as much as possible, and when I have to work on "my side", Itry to keep the angles such that the load would hit the groundbefore it reached me.�� I constantly think about "what can get me" orsomeone else.���� Of course when using this machine, people alwayswant to "help"...... I send them away.���� If I'm at the controls andsomeone else is at the end, there is a potential for me to injurethem.�� If I'm at the end and nobody is at the controls, there islittle or no danger..........You watch where you put your bodyparts.�� They are awfully tender!!���� I'm never casual aroundequipment, and always recognize the potential to make a mistake.�� Ican't afford to get hurt.�� I don't like getting hurt, and I don'thave workman's comp!



������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������ ������������ ������ ������ Howard

On 12/24/2012 04:32 PM, Gerald Feldman wrote:Thanks,Howard.�� I am reassured.�� After 39 years of working in ahospital, I just didn���t want to see anyone hurt.�� ��JerryF. ��From:funwithtransistors@yahoogroups.com[mailto:funwithtransistors@yahoogroups.com] OnBehalf Of StoneTool

Sent: Monday, December 24, 2012 3:55 PM

To: funwithtransistors@yahoogroups.com

Subject: Re: [funwithtransistors] NPN or PNPproximity sensor?







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