User Configuration without DIP Switches or Header Pins - Page 1
Forum section: electronics / projects

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 25, 2020, 11:03:26 pm
content: I often have the requirement to make a PCB that has to be configurable.... I have taken to creating a small footprint that allows the user to create a solder bridge for a selection of settingto be honest this doesn't work particularly well... the solder doesn't pool well to make a connection.An obvious alternative would be a set of DIP switches or Headers that allow a jumper pin but these are quite largeAny suggestions on making end-user configuration easy? (I am starting to wonder if my JP footprint is unreasonable due to being 0603 sized anyway... might not be feasible for anyone without a microscope?)

author: Bassman59
author_rank: Super Contributor
timestamp: July 26, 2020, 12:32:07 am
content: "End user" configuration means no soldering!What are you configuring? That might help us give a good suggestion.

author: TheMG
author_rank: Frequent Contributor
timestamp: July 26, 2020, 12:52:09 am
content: Some context would be helpful! What kind of thing is this configuring? Does the board include a microcontroller? What sort of maximum size constraint are we dealing with?

author: bson
author_rank: Unknown
timestamp: July 26, 2020, 05:46:50 am
content: How about50mil jumperson a small 50mil SMT pin header? 50mil is pretty small...Edit: a suitable header is Samtec FTSH-1nn-01-F-DV where 'nn' is the number of pins per row. (E.g., nn=02 for 2 pins per row, for 4 total.) FTS is the same, lower profile.(Yes, I know you didn't want headers or jumpers, but they do work nicely!)

author: Benta
author_rank: Super Contributor
timestamp: July 26, 2020, 10:06:58 am
content: Easiest and cheapest is an array of vias. Drill out the connections you don't want.Much faster than solder bridges.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 26, 2020, 10:17:47 am
content: Quote from: Benta on July 26, 2020, 10:06:58 amThis can be only modified once, from '1' to '0'. If this is acceptable, I would suggest using a very thin trace between fat pads, with no ground plane directly underneath, so that you can cut the trace with a knife. Mark where to cut by adding a solder mask cutout region right at the trace.But, it's too easy to accidentally remove the one bit you did not want to remove, especially if this "end user" isn't the assembler under your control.

author: OM222O
author_rank: Frequent Contributor
timestamp: July 26, 2020, 10:18:06 am
content: If your application uses a micro, doing it via a MUX or switch IC through software is the best solution. Especially if you have an ESP that allows control via wifi. Otherwise a gang of dip switches is unfortunetly the best. If the configuration is one time only, cuttable traces are the best.

author: Benta
author_rank: Super Contributor
timestamp: July 26, 2020, 10:34:24 am
content: Quote from: Siwastaja on July 26, 2020, 10:17:47 amInverting logic is the easiest thing in the world.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 26, 2020, 12:17:41 pm
content: Quote from: Benta on July 26, 2020, 10:34:24 amWat?The problem is you can't revert your decision. (Or need bodge wire + soldering iron to do that.)

author: tooki
author_rank: Super Contributor
timestamp: July 26, 2020, 12:41:45 pm
content: Quote from: NivagSwerdna on July 25, 2020, 11:03:26 pmWhy not just use 0 ohm jumpers (i.e. 0 ohm resistors)? They’re a common way of doing it.And if you really wanna get fancy, and happen to have a spare ADC pin on a microcontroller, you could use configuration resistors as a resistor divider, then measure the output voltage and configure based on that. That lets you use one fixed, preinstalled resistor plus a single configuration resistor to easily encode many different configurations.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 26, 2020, 12:43:27 pm
content: TH pad that can be drilled out, plus a pair of semicircular pads that can be solder-bridged to re-connectFor one-time configuration, I've seen a product that had a number of small fingers on the PCB, with U-shaped traces on, which were snapped off as requiredFor solder-blobs, a pair of 0805 pads with about a 0.5mm gap between them works well.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 26, 2020, 12:47:42 pm
content: And of course there are plenty of interactive methods using whatever switches and indicators you have available to store config in nonvolatile memory.touchpads are basically free if you don't have any buttons, and a single LED would do if there are only a few options, indicating via flash count/lengthsThis is something where you need to look at all your requirements to determine the best solution, e.g. do you need to be able to see the config when there is no power, can you (safely) power it for the user to do some sort of interactive process, what is the expected skill level of the person doing the config, could you use an external programmer box to do it etc. etc. etc.And is a DIP switch/link set more expensive than the support costs of a more arcane method ?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 26, 2020, 12:49:18 pm
content: Quote from: NivagSwerdna on July 25, 2020, 11:03:26 pmThat's a really poor layout for solder-blobbing. Use a pair of semicircular pads,at least 2mm dia, so the natural surface tension of the solder forms a dome over the 2 pads.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 26, 2020, 01:11:43 pm
content: Quote from: mikeselectricstuff on July 26, 2020, 12:49:18 pmThat's what I was thinking; in my design the solder tends to run back down the traces... very annoying... I think even with my design it needs more solder mask. I like the idea of semi-circular.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 26, 2020, 01:14:46 pm
content: Quote from: TheMG on July 26, 2020, 12:52:09 amOne example...I have a rather flexible ROM replacement board which fits in a 28 DIP package side... I need3x Bank Selection JP23x Address Selection JP27x Mode selection JP1JP2 is a jump that is either A or B; JP1 is either A or OPEN.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 26, 2020, 01:19:43 pm
content: Here's an example...Now there are several things that don't work here... firstly the JP2 solder options don't flow very well... and secondly this really isn't a practical method for end users... it's just too small and fiddly.Oh... and I do need the end user to be able to change these. <- Critical requirement

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 26, 2020, 01:25:12 pm
content: Quote from: bson on July 26, 2020, 05:46:50 amMaybe that is the answer.

author: mariush
author_rank: Super Contributor
timestamp: July 26, 2020, 02:04:58 pm
content: The footprint kinda sucks for jumpers.here's an example ... click on the picture ... See J1..J4 :https://www.digikey.com/product-detail/en/newhaven-display-intl/NHD-0216XZ-FSW-GBW/NHD-0216XZ-FSW-GBW-ND/2165850I've also seen basically the Yin Yang symbol -https://en.wikipedia.org/wiki/Yin_and_yang- with a bit of separation between the two sides ... a drop of flux and then a touch of solder and the surface tension would make good connection.Another reasonable option would be the footprints usually used for calculator and keyboard keys... something as simple as a U and E shape with the - between the U 's traces.ex a simplified version of this :https://electronics.stackexchange.com/questions/231293/studying-the-pcb-of-a-70s-calculator-what-were-they-thinkingor this : scroll down :https://www.petervis.com/Calculators/sharp-el-506h/sharp-el-506h.htmlFor a one time thing you could have 0 ohm resistors / jumper links ... make square/rectangular cutout in the pcb just big enough for the body of a resistor and put smd pads on the edges of the cutout ... have wire links or resistor across the hole in the pcb with leads soldered to the pads ... end user can just get scissors and cut the jumper link or resistor off.like people above told you ... you have 50mil (1.27) jumpers, you have 2 mm jumpers and headers, there's options.

author: phil from seattle
author_rank: Super Contributor
timestamp: July 26, 2020, 02:23:35 pm
content: I use both header/jumpers and solder connections (semi circular - 6 mil gap). dip switches take up too much space (and are so 1970s). The solder jumpers can be put on the bottom of a PCB so they are kind of "free" but at the cost of losing some users. I sell boards that require soldering so it's not a problem for my customers. 0 ohm resistors are basically the same as jumpers though larger and require a part - that's why I prefer jumpers.But, frankly, if you are targeting customers that can't solder, you probably should go a different direction - some sort of soft configuration.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 26, 2020, 04:01:34 pm
content: Quote from: phil from seattle on July 26, 2020, 02:23:35 pmI wonder what the least overhead soft configuration would be... I could add a very cheap small microcontroller to hold config (maybe not on the example above but on more complex designs)... but still would need some simple programming tool for the end user...

author: Benta
author_rank: Super Contributor
timestamp: July 26, 2020, 04:32:19 pm
content: I see you already use the leadframe pins, which are spring loaded (if you have the right size).How about placing pads on both sides of the PCB on the end edges, snip off the pins of your leadframe and slide the remaining "U-clip" onto there as jumper?

author: LateLesley
author_rank: Frequent Contributor
timestamp: July 26, 2020, 04:34:37 pm
content: Why not, instead of DIP switches, use those small SMD slide switches that you can get? Are they too big??https://www.aliexpress.com/item/32759141553.html?spm=a2g0o.productlist.0.0.5f905342MoJlpo&algo_pvid=5b3e7f13-f0b8-4639-9aa1-d02351d932ba&algo_expid=5b3e7f13-f0b8-4639-9aa1-d02351d932ba-21&btsid=0b0a22a415957808827705762e696d&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

author: ebclr
author_rank: Super Contributor
timestamp: July 26, 2020, 06:51:53 pm
content: 1.27 mm dipswitchs are smaller than your padshttps://www.mouser.com/Electromechanical/Switches/DIP-Switches-SIP-Switches/_/N-5g2s?P=1z0x3yz

author: bson
author_rank: Unknown
timestamp: July 26, 2020, 07:07:08 pm
content: If you use right angle, low profile, single row headers then you should be able to fit jumpers close to flat against the board.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 26, 2020, 07:58:06 pm
content: Quote from: ebclr on July 26, 2020, 06:51:53 pmThese are nice but I think that since they are only ON or OFF that would mean I need quite a few since a lot of my configuration is A-B or B-C rather than A-B or OPEN?

author: mariush
author_rank: Super Contributor
timestamp: July 26, 2020, 08:31:03 pm
content: Another idea would be to add a microSD connector or something similar .. you can get them as thin as 1.5mmex :https://www.digikey.com/product-detail/en/molex/1051620001/WM14405TR-ND/4555282or slightly thicker ones at 1.8mm that are hinged :https://www.digikey.com/product-detail/en/gct/MEM2067-02-180-00-A/2073-MEM2067-02-180-00-ATR-ND/9859613The microSD connectors have 8 or 9 contacts inside, which is great for 4 jumpers or more... so you could make a tiny square pcb and depending which side gets inserted, some contacts in the microSD are shorted or not, or connected to the 9th contact.If you make double sided thin pcb, you have 4 edges of pcb x 2 sides = 8 options.the tiny thin pcbs can be panelized so super cheap to make, the connectors are under 50 cents each in volume ... more expensive than jumpers but not very expensive.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 26, 2020, 08:41:22 pm
content: Quote from: mariush on July 26, 2020, 08:31:03 pmI like the lateral thinking... that's clever.