What's This Component?

Hi Jack,

Thanks for the quick reply and the links. Even though they're a non-stock item on Digi-Key, I can match characteristics and hopefully find ones that work.

Mike

Hello mike....

I feel it is potentiometer with variable resister. So you can vary the current by varying the potentiometer.

I am sure its a potentiometer with rating RXE110.

Have look over the circuit and analyse the importance of that potentiometer.

Suvek

It is a poly switch, follow link to see specification

http://www.alldatasheet.com/datasheet-pdf/pdf/147102/MACOM/RXE110.html

Steve

Mike,

We use these in our designs very often, so I know a little bit about them. What makes you think they are bad? Are they measuring open circuit?

Tom

Hi tdesmit,

I didn't say they were bad. I am designing a circuit and had never seen this schematic symbol before.

Mike

Hi tdesmit,

I won't argue that the symbol shown is also used for an MOV (the symbol shown just means "variable resistor, without mechanical adjustment"

Thanks for the reply. You just gave me exactly what I was looking for - not only what the device is, but exactly what the symbol means.

Thanks!

Mike

Tom Tdesmit,

That's worth a lot more 0.02 cents.

Especially the part about "t" or a "+t" next to it, to indicate that it's a temperature dependant variable resistor, the "+" indicating it's a PTC device. An MOV would have a "v" next to it, to indicate it's a "voltage" dependant variable resistor.

Having the RXE110 part number relaces the "t" or "V" function in the schematic.

Jon

Sorry, but this has long been one of my pet peeves!

$.02 is 2 ¢ (two cents), NOT 0.02 cents (two hundredths of a cent)!

Just yesterday, I saw fruit labeled .69¢ a pound (that's over 1.4 pounds per cent). I did refrain from insisting on buying some at that price...

Dick

Dick,

Good point.

I am going to look for those bargains from now on. If I win I can make some spare change by selling the excess to freinds and family.

Jon

I found one site that has the symbol of an MOV and a Thermistor. http://www.angelfire.com/electronic2/rch/schematic.html Also why does this device have pin numbers polarity? Seems strange an MOV and a Thermistor do not have polarity!

Having the pin numbers showing doesn't have to mean it's a polarized device, it's just a matter of how the schematic symbol is drawn. I hide the pin numbers on our schematic symbols for non-polarized passives, but some people show them.

Tom

Mav,

Numbering connections of non-polarized components on schematics is done for troubleshooting. It identifies where it is connected in the circuit and may relate to the PWB connection.

I often had to correlate the assembly connections to the schematic when doing analysis.

Jon

MOV Metal Oxide Varistor see link: http://en.wikipedia.org/wiki/Varistor

Mike,

They are, indeed Metal Oxide Varistor (MOV) symbols.

When they have a rated voltage applied for a certrain durating they protect the circuit they are designed into. As mentioned by another poster they act like an automatically recoverable fuse

Hi Mikerho,

On searching I found this similar drawing, is a thermistor, and another drawing this time with the short horizontal line at the bottom-left, is a Varistor.

It would make sense to combine these as a surge protection perhaps only accepting current from the electronics to the Motor and restricting current in the other direction. This may be pretty blooming obvious to you electronic experts and I do understand it. But my reading of the schematic is not at all good.

but, I cannot recall what a thermistor-varistor combination is called. Hope this makes sense.

Take care

A transducer which converts temperature (heat) to resistance (an electrical property).

There STILL seems to be some confusion over whether or not the device pictured is a MOV or a PPTC "polyswitch".

A MOV is a normally open shunt-connected protection device designed to conduct at a certain voltage and commonly used to shunt voltage spikes to ground protecting electronic components from excessive voltage. Think of it as a zener diode.

A PPTC (or commonly called by it's Tyco trademark "polyswitch") is a normally closed series-connected protection device designed to open at a certain temperature (relating to current) to protect an electronic device or load connected to it. Think of it as a self-resetting fuse.

As a final check look at the circuit these devices are used in in the original post. It's an H-bridge motor control circuit with the devices in question used between the motor drive circuitry and the motor itself. If they were normally open-circuit MOVs the motor would never operate!

http://en.wikipedia.org/wiki/H-bridge

Hopefully that clears things up.

Remember when looking at a problem, even a simple one (in this case "what does this symbol match?") don't forget to look at all the information given (specifically "how is the part being used?" and also "what part does its part number match").

Jack,

Clear, concise and accurate.

Jon

I agree with kudukdweller9. I gave you a GA. As of the time that I viewed this, he apparently hadn't yet...

I'd have to argue with the person who created the original drawing. It would seem that that person created the right half of the drawing, then reflected part or much of the right side to create the left side. The result is that the line passing through the resistor has the opposite slope. Unless I'm mistaken, the sloped line (together with the top and bottom lines) is intended to show a rough graph of the I vs E graph of the device. All four symbols should have the graph sloping down to the right.

DK,

Good observation. Lucky for that person that the part number RXE110 was included so a diagnostician would not be overly confused by the bad slope.

Jon

That would be some kind of variable resistor but not a POT. Without a part number it is hard to tell exactly.

This part is a resetable fuse. You can find this part on the net. It is a Tyco part.

RXE110 is the correct part number.

yup

http://pdf1.alldatasheet.com/datasheet-pdf/view/147102/MACOM/RXE110.html