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Topic: Is it possible to read 218 independent inputs? (Read 10329 times) previous topic - next topic


DigiKey has 25

Correct, I searched for 74597 assuming it would give me all types, HC/HCT etc but it doesn't.
Rob Gray aka the GRAYnomad www.robgray.com


farnell do have singles http://uk.farnell.com/texas-instruments/cd74hc597e/logic-shift-register-8bit-16dip/dp/1740104

(plenty more come up if you parametrically search for them)


Another near store has the CD4021 (US$1.30) (used on arduino shiftin docs (except the last "B")) and the 74HC165D "SMD" (US$4.00) (I wonder what SMD means).

The problem is that i'll have to travel a lot to the customhouse to take the shipment if I buy from Europe/USA.



Difficult to tell....

DigiKey will deliver  to everywhere..
Customs and Taxes - at least in Germany - will not be requested when the value is below 20 Euros and the adressee is not a company, and the parcel will be delivered by the PTT. Some persons even split their orders for that reason ...

You should by no means pay > USD 1 for those chips - just for principle :-)

SMD types will not help you at the moment...


Aug 16, 2010, 06:10 pm Last Edit: Aug 16, 2010, 06:40 pm by 2stl Reason: 1
Thanks deSilva.

The problem is, in my country, commercial shipments doesn't arrive at my house, and the customhouse is very far (4h by car). In theory, shipments below US$50 should not be taxed nor retained, but in practice things are very different. Even an Ubuntu CD was retained one occasion.

Maybe comparing the datasheets is a secure way to tell whether an IC is similar to another.

Just one more question... Is it possible to use the CD4021B instead of 74HC165? Or does it have some kind of linked ICs "limit" or something?



Aug 16, 2010, 07:11 pm Last Edit: Aug 16, 2010, 07:17 pm by mpeuser Reason: 1
The 4021 ist fine! I did not think of it because the 40 series has run out of popularity since the 74HC(T) chips came into existance. Valuable designs have been ported to that family, now called e.g. 74HC4051 wich is a very popular analog multiplexer.

The 4021 is - so to speak - some left over fossil... Its main advantage - as with the whole 40er series - is that it allows higher voltage (upto 15). Its disadvantage that it is not strictly TTL compatible, which however is not an issue in your application.


Thank you very much deSilva! However, I've found a local store that has the 74HC165! The guy said their stock is more than 10-year old, but it isn't a problem I think. I've bought 10 of them. Also, I am still waiting for my Arduino to arrive here (bought from a national importer).

Thanks!  ;)

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