Let’s be honest Trimmer Potentiometers (Trim pots) sometimes called “preset potentiometers” are not the most interesting component and ultimately most engineers agree you only want to use one if you really have to. They cost more than using set resistors, they take up space and time to adjust during manufacturing if you use them in a professional product, but for the times when using one is a must using the right one in the right way can be important. Below is a small overview of the most commonly used types of Trimmer Potentiometers.
Types of trim pot
RM065 / 3318 – A very cheap and cheerful through hole trim pot. The 065 type is the horizontal version and the 063 is vertical. The original manufacturer seems to be Runtron. There seems to be a more sturdy version made by Bourns called the 3318F that uses more metal. The datasheet for the RM065 / RM063 can be found here.
Pros: Cheap, easy to find, small ish footprint (about 6mm long), available as cheap chinese knockoffs or genuine parts.
Cons: Semi open frame makes them susceptible to dust and dirt ingress, not super reliable, unsealed.
3362 – My personal choice if I need to use a single turn through hole trimmer. A great option to use if you need a sealed, single turn, through hole trim pot. The 3362 series are cheap, widely available and very reliable. 3362s come in a wide variety of variants 3362P/M/S/X/W etc like meany parts the letter at the end of the part number denotes the variant. The datasheet for the 3362 can be found here.
Pros: Cheap, very reliable, easy to find, small ish footprint (Just under 7x7mm) available as cheap chinese knockoffs or genuine parts, fully sealed so they can be locked with locking epoxy.
Cons: Can’t think of any..
3296 – This is my personal choice if I need to use a multi turn through hole trimmer. Probably the best choice if you need a multiturn trimmer as the SMD version tends to be very expensive. I would really recommend buying genuine 3296es as the fakes tend to be rubbish, I’ve even had issues the genuine Suntan brand parts bought from Rapid electronics having dead or scratchy spots, I have found the best brands tend to be BI and TT electronics. It is important to remember that 3296es and there other compatible parts come in 10, 12 and 25 turn versions and some fake 3296es sold as 25 turn but can be as low as 5 turns ! There seems to be an odd version of the 3296 that’s only available in china that makes it adjustable by hand called the 3296W-B made by the company BOCHEN. The datasheet for the 3396 can be found here.
Pros: Fairly cheap If you know where to look, reliable, fully sealed so they can be locked with locking epoxy, they come in a wide array of variants.
Cons: Chinese knockoffs are of very low quality, the W type is quite tall and sticks out.
(3296W) (3296W–B) (BI / TT electronics Grey 3296W)
3×3 / 3*3 / 3304W / TC33 / EVM3ESX – 3×3 (3mm by 3mm) type trimmers are an excellent choice if you need a very low cost small, single turn SMD trimmer. They go under a few different names but I tend to go for the EVM3 type made by panasonic however these are set to be discontinued by 2019 so I would recommend the TC33 series made by bourns.Using a proper trimmer adjustment tool such as a bourns h-90 is a must with this type of trimmer ! The datasheet for the TC33 series can be found here.
Pros: Very cheap, super small, SMD, they work with cheap desktop pick and place machines.
Cons: Hard to solder (neatly) without solder paste, susceptible to dust and dirt ingress. You can’t lock them with locking epoxy.
3314 / 5×5 – 3314s are single turn sealed SMD trimmers that are a nice upgrade from the 3×3 type. The have the benefit of being sealed meaning they are more reliable and can be locked with locking epoxy. The letter at the end of the part number seems to denote the lead style. The datasheet for the 3314 series can be found here.
Pros: Small (5 by 5 mm) and SMD, reliable, sealed.
Cons: Expensive, good temperature control is needed when soldering using an oven or hotplate.
3224 – Probably the only viable choice if you need an SMD multi turn trimmer as similar options are extremely expensive. I can’t say i’ve ever used this type but they look good. The datasheet for the 3224 series can be found here.
Pros: Small and SMD, reliable, sealed, multi turn.
Cons: Very expensive !, good temperature control is probably needed when soldering using an oven.
Where to find Trimmer Potentiometers
(The usual suspects).
For cheap knockoffs and sometimes factory rejects of genuine parts or even just cheap tax free genuine parts check out the following:
For genuine and reliable branded parts that are probably more expensive check out:
Gunk – Putting a dab of paint or loctite on a trimmer is often used as an anti-tamper method or vibration mitigation in places where a trimmer may be messed with or get moved by something like the simple act of shipping.
(Electrolube BLV15ML) (RS Pro Epoxy Coating)
It’s also a good idea to buy a high quality trimmer adjustment tool as it helps reduce slipping, I use a bourns h-90.
Some good reading about trimmers !
Trimpots with 0.1 Inch Lead Spacing by robotroom.com
Trimpots by resistorguide.com