Cumulative Design Review

Component scarcity

Component scarcity

by Svend Haugaard -
Number of replies: 8
PCBs received from JLCPCB but the global component scarcity is close to put my project on hold as the rotary encoders and the LED driver are currently not in stock in Europe. Suppliers have some in stock in the US and China but component prices and shipment surplus is too high for this little project.

Others having same issue?

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In reply to Svend Haugaard

Re: Component scarcity

by Mark Hughes -
Well that's certainly sad to hear Svend. Have you checked alternate suppliers? Arrow, Mouser, Rutronik, etc.? Even if you can't find the part number in question, you might find one with a different part number. Sometimes companies will whitelabel a product and it'll appear with other MPNs.

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In reply to Mark Hughes

Re: Component scarcity

by Henri Kemppainen -
Would TI SN74HC595PWR work as a pin-compatible alternative for the LED driver? Output current may be lower so one would have to increase the resistors a bit and you'd get lower max brightness but I don't know if that's a showstopper. (I don't personally see the need for blinding bright leds in a keyboard)

https://www.ti.com/lit/ds/symlink/sn74hc595.pdf

Farnell claims to have over 6000 of these in stock but IDK if they sell to individuals without VAT id :( I haven't had much luck with European distributors in general.

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In reply to Henri Kemppainen

Re: Component scarcity

by Mark Hughes -
If it is a pin-compatible replacement, you're good to go. The 595 has been around since the 80's. Don't even need to adjust the current limiting resistors.

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In reply to Mark Hughes

Re: Component scarcity

by Svend Haugaard -
Yes I checked several suppliers but none has all needed parts or alternatives in stock. Some parts they offer to ship from their US stock at a surplus of 200 DKK / 30 USD on top of the normal shipment costs. So I can get the parts but the project will just be too expensive for its purpose. For now, Mouser is best option. However, stocks are volatile so I follow up :-)

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In reply to Svend Haugaard

Re: Component scarcity

by Henri Kemppainen -
If SN74HC595PWR seems suitable for you (please double check datasheet or find someone who can help with that?), tme.eu claims to have some in stock: https://www.tme.eu/en/details/sn74hc595pwr/shift-registers/texas-instruments/

If you search for 74hc595, you may find other possible alternatives in their catalog.

They also seem to have a few pieces of some variant of PEL12T in stock: https://www.tme.eu/en/details/pel12t-4226f-s1024/incremental-type-encoders/bourns/

I can't remember what the difference between all the variants is so again double check, but at least the product image looks very similar to what I've got.

I have no experience buying from tme.eu but it seems they're located in Poland (and have offices in many countries in Europe) and also appear to do business with individuals.

Let me know if this works out for you!

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In reply to Henri Kemppainen

Re: Component scarcity

by Henri Kemppainen -
Well, Jesse pointed out SN74HC595PWR is unfortunately not a drop-in replacement for NLSF595 because it's got push-pull outputs rather than open drain outputs so it may not fully turn off leds at 3.3V and running it at 5V would require level translation.

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In reply to Henri Kemppainen

Re: Component scarcity

by Jesse Robinson -
I don't think that would be compatible, how we are currently using the NLSF is using 3.3V logic but sinking 5V powered LEDs, taking advantage of its open drain outputs with over voltage tolerance. The TI part is CMOS so it does push/pull, meaning it will output 0V or 3.3V, meaning your LEDs sourced from 5V wouldn't turn all the way off when you set the output high. It could be made to work, like using it to drive transistors or tying to 5V logic and using level translators, but those are design changes at the schematic level.

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In reply to Jesse Robinson

Re: Component scarcity

by Svend Haugaard -
Confirmed, the 74HC595 is not a drop-in replacement for the NLSF in the existing design.

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