A discussion came up on the Hackaday Discord PCB design channel about resistor networks, and it got me thinking about whether we (the hacker community) use them in designs or not. These handy devices often take the shape of an IC, SMD or otherwise, but between the pins are a bunch of resistors instead of active silicon. They come in all sorts of configurations and tolerances, but the point is usually the same: When you need a bunch of similar resistors, it’s cheaper to go with a network package.
But how much cheaper? I did a quick search for 1 kΩ resistors and the corresponding network, and came up with similar prices for the resistors and networks – but the network has eight resistors in it! That’s an eightfold savings! Which, at a price of roughly one cent per piece, is less than a dime. While it’s certainly true that if you’re making a million widgets, saving a penny per widget matters. But do you spend the time to optimize your projects down to such margins? I want to say “of course not!” but maybe you do?
For me, worrying about seven cents in a PCB design that I may make ten of is foolishness. But still, I’ve used resistor networks for their other side effects: the resistors in a common package tend to be very tightly matched, even if their overall tolerance isn’t. If you’re making something like an R-2R DAC, that’s a definite advantage. Or if you’re space constrained, or just hate placing lots of tiny resistors, the networks shine.
I often forget about resistor networks, and when I do think of them, I think of them in terms of cost savings in industrial applications. But maybe that’s not fair – maybe they do have their hacker uses as well. Are there other parts like this that we should all know about?
And how about assembly costs. Will a single chip versus 8 much smaller chips save time and effort with putting things together?
Just wanted to comment about how much I like the title to the story! :)
Certain amount of flexibility in that untapped quantity in that any future changes could be made easier by being already there.
Assembly costs! Its quicker and easier to solder one component than eight. Especially true in hand-placement of components, but still true in fully automated assembly.
But it is cheaper to place 10 of the same then 2 different ones.
And consider that you may have to pay to load the assembly machine with a new fairly unique part, versus using standard resistors already loaded into the machine.
Resistor networks new and unique? That’s news to the electronics industry.
PnP costs a penny per (flyshit) part, assembly costs it doesn’t matter enough.
Resistor arrays mainly save PCB real estate. The 4 or 8 in 1 is popular, especially for pull-up resistors kind of use. You get less power dissipation with 4 resistors in one small package though, must use common values and they tend to be made by fewer companies so they go out of stock easier.
They were a big deal in the 80’s in DIP or SIP package and cost more than discrete resistors.
Yeah, I was going to say the same thing – Real Estate. Just designed a PCB yesterday with diode arrays as there was no space for 6 individual items. Personally, dont care about cost as all my stuff is dev not prod.
They are mighty useful for bus termination where many parallel traces need to be terminated into a common ground. They save loads of space and time!
Recently developed a board with DDR3 RAM, there’s no way in hell I’m placing roughly fourty 0402 resistors on the backside of the PCB when I can also place 2 or 4 resistor arrays.
yeah that’s what i was going to say…i couldn’t detect the cost but when i’m laying something out for hand assembly (which isn’t often), i’ve wanted resistor arrays simply because they happened to fit shape of my requirements so perfectly. i had pins in a row that needed terminating and here is a component that is a row of terminators!
Another advantage is that the resistors on a network resistor package are also tightly thermally coupled to each other. Thus when temperature drift occurs, all the resistors will drift together as a group.
I ended up going back and forth with this waaaay longer than made financial sense for my 100 board project. The Asian branded networks and arrays I looked at didn’t make financial sense in the end. 8 resistors in 1 package is still 16 joints – and my manufacturer charges per joint, besides pr part.
The part I would’ve like to use had 8 resistors with a common pin in a 10 pin SMD package – but at qty 100-400 it was 8 cents. And 5% 0603’s are 0.1 cents. 10x cheaper for singles.
I did end up going with 4×1 resistor arrays at about the same price, simply to make things fit. 7 packs are easier to fit than 28 0603’s.
I could’ve gone 0402 instead – but that’s a different can of worms.
I design around sip resistor packs because I’m spending down the contents of an electronics goldmine surprise box. That and you can easily make a sip resistor pack by hand if you have individual resistors. (My boards only need to be hand assemble-able, and I only need to have enough parts to make 5 to justify having boards made)
Wow! I’m surprised that so many people use ’em, but for all the right reasons! :)
Space, tolerances, tempco, etc. Very cool! Maybe I’ll try to work them in more, just because.
Thanks all who responded!
The terms are used in reverse, from my point of view.
By “optimization” I understand enhancing reliability, longevity and functionality of a given circuit or product.
Investing labor and money to make it better, in short.
Which in turn could have a positive effect on my reputation, if my stuff lasts and needs little to no servicing (customer is happy; also means less stress to me, as well; win-win situation).
But this article seems to be about cost minimization, though, which more than often is the exact opposite. Anyway, these are just my two cents. No more, no less. Happy Easter, everyone. 🙂🐇
Resistor networks aren’t going to always be a drop in for replacing several other individual resistors depending on your design. They are typically used for pulling data buses high or low, this is why they generally come in multiples of 8. Other uses might be the current limiting resistor for 7 segment LEDs, bar graph LEDs, or several individual LEDs.
But I can buy a few resistors while I have to buy a minimum of the surface mount resistor packs. So the resistor pack may be 1 cent. when you go to buy a minimum of a 1,000 or whatever it is. verse the 10 or 20 you have to buy of the through whole resistor. or are you comparing surface mount to surface mount?
HLK88 slot When numerous parallel traces need to be terminated into a common ground for bus termination, they are quite helpful. They save so much time and space!
I recently designed a board with DDR3 RAM, and there is no way in hell that I’m going to insert two or four resistor arrays instead of about forty 0402 resistors on the rear of the PCB.
“But how much cheaper? I did a quick search for 1 kΩ resistors and the corresponding network, and came up with similar prices for the resistors and networks ”
And not only for custom PCB’s. When designing for mass production, it’s a matter that you need to mount 1x piece or 8x piece on the SMD assembly machine.
Every package and component has its own use case, exists for a reason. Engineer’s work is to harness the power of it in their favor.