Where to buy cheap logic?

[joedino]

Hello all. 

 

Short version: I need to buy cheap digital logic ( and, or, not, nand, nor, xor). Where is the best place for this?

 

Longer version: i am planning on building a simple, 2 or 4 bit, alu/cpu for an electronics club at college. I really want to make it out of discrete logic (other than memory). I know that this is "the hard way" and it will be "a lot of soldering" but that is part of the fun. Let me know what you think and if you want updates on the project. 

[Mira Yurizaki]

Out of curiosity, have you looked at Digikey or Mouser?

[joedino]

7 minutes ago, M.Yurizaki said:

Out of curiosity, have you looked at Digikey or Mouser?

that's a negative 

[Sauron]

19 minutes ago, joedino said:

that is part of the fun

Just a thought - at that point why not go full hardcore and build it out of single MOS transistors?

 

As for buying logic gates, those (like most small electronics) are usually bought in bulk, so finding them singled out at a cheap enough price to build an ALU out of them might be a challenge. If you are part of a specialized club, perhaps you should try convincing the other members to make a bulk order and split the cost.

[Mira Yurizaki]

1 minute ago, joedino said:

that's a negative 

You should look at those two suppliers. I'm not sure how cheap they'll be (especially if you don't buy in bulk), but it should at least give you a baseline for parts.

[joedino]

1 minute ago, Sauron said:

Just a thought - at that point why not go full hardcore and build it out of single MOS transistors?

 

As for buying logic gates, those (like most small electronics) are usually bought in bulk, so finding them singled out at a cheap enough price to build an ALU out of them might be a challenge. If you are part of a specialized club, perhaps you should try convincing the other members to make a bulk order and split the cost.

Buying bulk is fine. I'm planing on doing a lot of this kind of stuff

[Sauron]

4 minutes ago, joedino said:

Buying bulk is fine. I'm planing on doing a lot of this kind of stuff

Alibaba may be a good place to start if you don't mind importing from Asia.

[Lolucoca]

ebay, look for logic ic collections, I just picked up 450 logic ICs for 5 bucks

[Unimportant]

On 8/24/2017 at 9:15 PM, Lolucoca said:

ebay, look for logic ic collections, I just picked up 450 logic ICs for 5 bucks

Seems there's some counterfeiting going on there tough, when ordering from china. Read Ken Shirriff's latest blog post if interested (well, you should anyway - it's a good read)

http://www.righto.com/2017/08/inside-fake-ram-chip-i-found-something.html

 

@joedino

We use Farnell as our supplier, they should carry all the 40 series/74 series but I don't think you can buy there as a normal, non-business, consumer - altough your college might be able to help place a order ? Thumbs up for "learning it the hard way". These skills can remain applicable, for example when using FPGA's.

[Lolucoca]

You're going to have to use some combinational logic when working with microprocessors. You could cut down on the cost and use a parralel EEPROM. 

[Coaxialgamer]

On 8/24/2017 at 5:33 PM, Sauron said:

Just a thought - at that point why not go full hardcore and build it out of single MOS transistors?

 

As for buying logic gates, those (like most small electronics) are usually bought in bulk, so finding them singled out at a cheap enough price to build an ALU out of them might be a challenge. If you are part of a specialized club, perhaps you should try convincing the other members to make a bulk order and split the cost.

I attempted to use single transistor to make adders at one point. It's just too much work, and you have to deal with a lot more "analog" issues when working with discrete stuff than just using logic IC's. Plus, wiring is much harder to keep track of. 

Plus, OP will have to go for ICs at one point anyway, considering that each byte of SRAM uses 52 transistor. 

 

To OP : Try ebay or amazon. I've had luck with a brand called sodial, which sells this type of stuff for dirt cheap ( bough 100 S8050 BJT transistors for less than 2$) if you're okay with waiting 3 weeks for them to arrive. 

You can also check out digikey or mouser. They usually offer discounts on larger quantities. 

[mariushm]

Digikey , Mouser, Farnell / Newark (they use newark.com for US/Canada and some countries, Farnell.com for others) , TME.eu (european distributor) .. these are the major ones I worked with , and which are relatively hobbyist / private person friendly as in they allow buying small quantities with simple order processes (no faxing orders or signing invoices through fax, or ordering 100pcs minimum, crap like that) and relatively cheap shipping costs.

 

I could mention some other websites especially a chinese store which often lists components for super low prices but it's a luck thing.  How could I explain... often they list some part in stock and you order it along with others and maybe two weeks later you may think the package is on its way but if you ask about your order they'll say they're still waiting on a new batch of that part to be stocked and then they'll ship to you.

 

It costs more to buy from these online distributors but it's worth it, they're a very high confidence you'll get genuine parts. It's rare but even these big official distributors still get clones from time to time but super rare and usually for more profitable chips)

In contrast, on eBay you'll often get parts which are harvested from broken/old hardware (not a bad thing in itself, but you don't know how many heat / cool cycles that part was subjected to, or how humid the environment was and for some parts this matters) ...

... or parts that have their text rubbed off and rewritten to show a newer manufacturing date, or newer revision of some chip or ...

...they're parts fabricated in Chinese fabs with worse specs (but still within acceptable limits genuine parts are supposed to tolerate) and then they write the logos of the genuine part (like for example genuine part should work with 2.5v..6v  but clone part would only work with 4v .. 5.5v 

 

[ostrops]

I would also recommend Jameco electronics and, for small quantities, Sparkfun (they are overpriced).