Do 2-lug series resistance trimmers exist?

Nitefly182 · January 31, 2009, 04:15:21 PM

I want to drop some trimmers onto a board but I would like to not use a regular trim pot since they just wont fit. Does anyone know if trimmers are available that are meant for simple series resistance that could drop right in place of a resistor?

R.G. · January 31, 2009, 04:36:15 PM

Not to my knowledge. In over 35 years I've never seen one. Doesn't mean they don't exist somewhere, but it's likely to be easier to re-do the board than to find one.

Cliff Schecht · January 31, 2009, 04:50:33 PM

Take a look at some of these:
http://mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsDYiCshOPiYOMpHYjMuonuhFZobW%2fO0KI%3d
http://mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsDYiCshOPiYG3OJ0t4qA7GuAk3uL66zvM%3d
http://mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsDYiCshOPiYGdwA0ev8dcY7sDYsxcTQ6E%3d
http://mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsDYiCshOPiYN8d3fQ1ewY776HJprFNZQc%3d
http://mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsDYiCshOPiYPRStzRepRFHLJblNhrOHfs%3d

If none of these fit, you can also take a look at SMD solutions, I think they make trimpots down to about 3 mm. If you can't fit that, then you're asking too much of potentiometer manufacturers

.

Nitefly182 · January 31, 2009, 05:06:15 PM

Quote from: Cliff Schecht on January 31, 2009, 04:50:33 PM
Take a look at some of these:
http://mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsDYiCshOPiYOMpHYjMuonuhFZobW%2fO0KI%3d
http://mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsDYiCshOPiYG3OJ0t4qA7GuAk3uL66zvM%3d
http://mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsDYiCshOPiYGdwA0ev8dcY7sDYsxcTQ6E%3d
http://mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsDYiCshOPiYN8d3fQ1ewY776HJprFNZQc%3d
http://mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMsDYiCshOPiYPRStzRepRFHLJblNhrOHfs%3d

If none of these fit, you can also take a look at SMD solutions, I think they make trimpots down to about 3 mm. If you can't fit that, then you're asking too much of potentiometer manufacturers .

I just saw those and I think they will work really well since I can just clip the extra lug off. I'm building a tonebender with the original layout and dropping a 20k trimmer in place of the bias resistor and this should be perfect. Thanks!

Cliff Schecht · January 31, 2009, 05:09:04 PM

It's good to tie off that third lug the the center tap instead of leaving it as a floating node. Since you're using it in place of a resistor, just bend two leads (the middle lug and one of the outsides gets tied together) one way and the third lug goes the other way.

Nitefly182 · January 31, 2009, 05:19:19 PM

Quote from: Cliff Schecht on January 31, 2009, 05:09:04 PM
It's good to tie off that third lug the the center tap instead of leaving it as a floating node. Since you're using it in place of a resistor, just bend two leads (the middle lug and one of the outsides gets tied together) one way and the third lug goes the other way.

Good call. And it would probably be easy to just drop lugs 1 and 2 into a pair of holes on one strip to keep things neat.

Cliff Schecht · January 31, 2009, 07:08:28 PM

Quote from: Nitefly182 on January 31, 2009, 05:19:19 PM
Quote from: Cliff Schecht on January 31, 2009, 05:09:04 PM
It's good to tie off that third lug the the center tap instead of leaving it as a floating node. Since you're using it in place of a resistor, just bend two leads (the middle lug and one of the outsides gets tied together) one way and the third lug goes the other way.

Good call. And it would probably be easy to just drop lugs 1 and 2 into a pair of holes on one strip to keep things neat.

Exactly! I was going to recommend that but I see you get my point

.

analogguru · February 01, 2009, 06:18:52 AM

Quote from: R.G. on January 31, 2009, 04:36:15 PM
Not to my knowledge. In over 35 years I've never seen one.

Really ? Then here is your chance to see them the first time:

I highly doubt, that they are still available.
The examples shown above were made by ISKRA in former yugoslavia.
The german company PREH produced them too.

analogguru

R.G. · February 01, 2009, 08:46:38 AM

Cool! I've never seen those. Perhaps they were only available in Europe. My experience is limited to US electronics and Japanese stereo stuff. We didn't get much European gear.

Nitefly182 · February 01, 2009, 02:13:41 PM

Se it seems like those would be relatively easy for a company to make in a small package for things that need to be biased in general electronics. Of course, most products probably dont need any biasing so its not as useful as I think.

R.G. · February 01, 2009, 03:39:55 PM

EEs are awarded DEmerits if they put any trimpots in a design. Trimmers have to be trimmed, and it's one mark of a good design for the circuit not to need trimming. Trimming requires a human with some kind of meter or scope to look at every unit and tweak it in. Then you have to worry about pot life, reliability, drift, tolerances, and users turning the trimpots in a fit of BUMS (Blind Urge to Mod Syndrome). Engineers designing circuits which must have two or more trimmers are fired.

andrew_k · February 01, 2009, 04:18:09 PM

Quote from: R.G. on February 01, 2009, 03:39:55 PM
Engineers designing circuits which must have two or more trimmers are fired.

A/DA Flanger

earthtonesaudio · February 01, 2009, 10:55:37 PM

Quote from: R.G. on February 01, 2009, 03:39:55 PMEngineers designing circuits which must have two or more trimmers are fired.

...But Danelectro will never clone one of their trimmer-full circuits.

Cliff Schecht · February 01, 2009, 10:59:45 PM

Quote from: R.G. on February 01, 2009, 03:39:55 PM
EEs are awarded DEmerits if they put any trimpots in a design. Trimmers have to be trimmed, and it's one mark of a good design for the circuit not to need trimming. Trimming requires a human with some kind of meter or scope to look at every unit and tweak it in. Then you have to worry about pot life, reliability, drift, tolerances, and users turning the trimpots in a fit of BUMS (Blind Urge to Mod Syndrome). Engineers designing circuits which must have two or more trimmers are fired.

Same goes for jumpers. I guess it's more of a draftsman skill but people who use excessive jumpers should go back to PCB design 101!

R.G. · February 01, 2009, 11:32:41 PM

Quote from: Cliff Schecht on February 01, 2009, 10:59:45 PM
Same goes for jumpers. I guess it's more of a draftsman skill but people who use excessive jumpers should go back to PCB design 101!

Yes - for excessive jumpers.

However, I once talked myself out of a tight spot by pointing out that the complete cost of the jumpers (component cost, insertion, engineering records, inventory, failure rate and warranty costs, fully burdened) was less than the cost of adding a second layer. Got an attaboy instead of a dressing down. That was one of my early self lessons in everything having a cost, even not doing something. It came in handy later as a way to look at things.

But jumpers and vias where not needed should raise snickers at least.

Cliff Schecht · February 02, 2009, 01:44:49 AM

Quote from: R.G. on February 01, 2009, 11:32:41 PM
Quote from: Cliff Schecht on February 01, 2009, 10:59:45 PM
Same goes for jumpers. I guess it's more of a draftsman skill but people who use excessive jumpers should go back to PCB design 101!
Yes - for excessive jumpers.

However, I once talked myself out of a tight spot by pointing out that the complete cost of the jumpers (component cost, insertion, engineering records, inventory, failure rate and warranty costs, fully burdened) was less than the cost of adding a second layer. Got an attaboy instead of a dressing down. That was one of my early self lessons in everything having a cost, even not doing something. It came in handy later as a way to look at things.

But jumpers and vias where not needed should raise snickers at least.

A lot of the stuff Simonton did was single sided with a crap ton of jumpers, up until the 9700 series synths that pretty much had to be double sided. I understand the price margin between a single sided board with jumpers and double-layer board, and this becomes especially important when one is trying to meet a certain price point. A good example of this is the Fatman, the board has 43 jumpers that the user has to stuff. Stuffing these jumpers takes longer then doing the resistors and the capacitors, but at the same time this style of construction is one of the reasons the thing is so cheap.

earthtonesaudio · February 02, 2009, 08:48:09 AM

If you have a single sided board with mixed surface mount and through-hole construction, do you get bonus points for using the through-hole components (or their leads) as jumpers?

Cliff Schecht · February 02, 2009, 01:24:18 PM

Quote from: earthtonesaudio on February 02, 2009, 08:48:09 AM
If you have a single sided board with mixed surface mount and through-hole construction, do you get bonus points for using the through-hole components (or their leads) as jumpers?

Yes! Get clever, that's what separates a good engineer from a "textbook" one

.

analogmike · February 02, 2009, 01:48:15 PM

Quote from: earthtonesaudio on February 02, 2009, 08:48:09 AM
If you have a single sided board with mixed surface mount and through-hole construction, do you get bonus points for using the through-hole components (or their leads) as jumpers?

Cliff Schecht · February 02, 2009, 04:59:37 PM

Quote from: analogmike on February 02, 2009, 01:48:15 PM
Quote from: earthtonesaudio on February 02, 2009, 08:48:09 AM
If you have a single sided board with mixed surface mount and through-hole construction, do you get bonus points for using the through-hole components (or their leads) as jumpers?

Heck, even using 0 ohm resistors looks better than a multitude of jumpers. Dunlop is one company I know of that uses this approach (although they use mostly SMD components in their new stuff).

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Do 2-lug series resistance trimmers exist?