Why do variable resistors have such short leads?

[z-adamson]

Diodes, resistors, capacitors, transistors..............all have long leads to trim down after installation.

Variable resistors......ie. Bourns 3296 series multiturn variable resistors......have very short leads making them difficult to use sometimes without soldering extensions onto the leads.

I can't think of any advantage to this.

Why don't they make them long with the idea that the leads will be cut down after being soldered into place on the PCB as is the case with just about all other components?

 

[sKiZo]

The VRs of which you speak are typically used on circuit boards and don't really need the extra length. Caps, resistors, and such are more universal, able to be boarded or point to point connections.

PS ... you can make the leads on these as long as you want, eh ... <G>

 

[Blue Shadow]

If you mount a long leaded vr and twist it past its end points you risk having the long leads touch. Not good, no longer a variable resistor.

The legs seem short because we use the new ones to replace different styles that may have different spacing and that means we gotta bend the leads to work.

 

[audiodummy]

The Bourns 3296 multiturn pot was meant specifically for mounting on PCBs and only PCBs, and since it's only for a PCB adding longer leads just costs money that the end user will just trim off. Not like ¼W or ½W resistors at all which are frequently point to point freehanded, hence the longer leads.

It's the equivalent of asking for longer leads on DIP14 ICs so people can dead bug or freehand.

I suspect that TO-220s and other transistors are a middle ground. People do freehand these as well as put them in PCBs, hence their pins are a bit longer than typical PCB only devices.

 

[BinaryMike]

With some of these little trimmers, the normal adjustment torque would be enough to bend the leads if they were longer.

 

[z-adamson]

The Bourns 3296 multiturn pot was meant specifically for mounting on PCBs and only PCBs, and since it's only for a PCB adding longer leads just costs money that the end user will just trim off. Not like ¼W or ½W resistors at all which are frequently point to point freehanded, hence the longer leads.

It's the equivalent of asking for longer leads on DIP14 ICs so people can dead bug or freehand.

I suspect that TO-220s and other transistors are a middle ground. People do freehand these as well as put them in PCBs, hence their pins are a bit longer than typical PCB only devices.

The solder pad spacing can vary from one PCB to the next and as such longer leads come in VERY handy as the spacing from solder pad to solder pad increases. Don't need the length, cut it off. If you need the length due to spacing, then you are good to go.

Thats my thought anyways.

 

[z-adamson]

With some of these little trimmers, the normal adjustment torque would be enough to bend the leads if they were longer.

It would be ideal for the extra length to go through the PCB to the solder side then get cut off rather than hanging out on the component side creating space between the trimmer and the PCB. The closer the trimmer to the board, the less of an issue bending the leads is.

 

[audiodummy]

These units were designed for OEM, not for retrofit/replacement. They assume the vast majority of these units will be soldered straight into a board that was designed with them in mind with fresh solder and pads that match - which also solves the torque problem when the body of the pot will be flush to the board with no gap. Yes, there will be a few designs with last minute ECOs due to lack of a different part, but who's the poor soul that needs to bend leads and manually solder them in.

We're using them for retrofit/replacement/one-off designs, hence we're complaining. The number of these uses combined is theoretically dwarfed by the original designs they want to target with matching PCB footprints and automated pick&place insertion, else they would have come with longer leads (or you could find more expensive larger units with solder eyes on them... if they still make them!)