Jellybean logic gates? - Page 1
Forum section: electronics / beginners

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 12, 2016, 04:41:57 pm
content: Any jellybean logic gates to recommend? Preferably something I can 'grab-and-go' when I need it and stockpile, and cheaply available on aliexpress/evilbay by the hundreds. I'm mostly working on lower voltage/current projects now (~3-5v).Currently, I'm using 2N3904s as makeshift gates, however they gobble up too much current for my liking (for instance, a 3904 configured as a NOT gate consumes 50ma of current on standby). I've never really looked into logic gates seriously before this.Unfortunately, Googling for it turned up entirely differing results from what I need:Thanks in advance!

author: rrinker
author_rank: Super Contributor
timestamp: January 12, 2016, 04:47:50 pm
content: Yeah Google can have problems when it's really a slang term. Funny thing, first hit I got for "jellybean op amp" is this thread. Second is another thread on this forum.I can't make any specific recommendations, it's been a long time since I did lots of logic design, and since my first computer was an all-CMOS design, I always had lots of 4000 series CMOS at hand. I'm not even sure what the current goodness is - 74HC series? Since you can make anything out of NAND or NOR gates, you'd probably want lots of those, plus some invertors.

author: Kjelt
author_rank: Super Contributor
timestamp: January 12, 2016, 04:58:21 pm
content: If smt is not a problem check out the single gate packages from nxp, they are available in sot package size but now even extremely smaller.I like to have a few of each in stock just if i need a single nand or nor or whatever function.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 12, 2016, 05:01:24 pm
content: The two main series als the old CMOS4000 (e.g. HEF40xx, CD40xx,... depending on maufacturer) series and the 74HCxxx series. The 4000 series is slow but works to higher voltages (e.g. 12 V) and with only low output current. The 74HC... generally is for 2-6 V, but are faster and can drive more current (e.g. LEDs). There are other similar series for higher speed, lower power, lower voltage and so on - but faster than 74HC... allready gets problematic on a vero board as they need good decoupling. Usually one can mix them if the supply matches.

author: mikerj
author_rank: Super Contributor
timestamp: January 12, 2016, 05:02:50 pm
content: Quote from: thejoggingmat on January 12, 2016, 04:41:57 pmThat sounds way too high, what value of collector resistor are you using?

author: mngiggle
author_rank: Contributor
timestamp: January 12, 2016, 06:09:53 pm
content: Also if SMT isn't an issue, it might be worth looking up some configurable logic gates (at least NXP and TI have them, probably others as well) to avoid stocking too many different ICs.

author: Audioguru
author_rank: Super Contributor
timestamp: January 12, 2016, 06:13:58 pm
content: A Cmos CD4069 logic inverter (called a NOT gate when it is not a gate?) draws such a low current when its output is high or low that you will not be able to measure it.It draws some current when it is switching a high frequency because then its current is charging and discharging stray capacitances.Here are two logic inverters made with a transistor (I forgot to include the base current for the transistor):

author: rdl
author_rank: Super Contributor
timestamp: January 12, 2016, 07:08:50 pm
content: Try searching for something closer to what you're looking for...cmos logic jelly beanttl logic jelly bean...for example.

author: dentaku
author_rank: Frequent Contributor
timestamp: January 12, 2016, 09:26:11 pm
content: The word jellybean is throwing off your search results.Maybe if you look at a logic simulator like this you can find what you might find the most useful and then order some cheap 4000 or 7400 series chips from ebay that do those functions.http://www.neuroproductions.be/logic-lab/This site has come in handy for me when messing with old 4000 series logic chips too.http://www.doctronics.co.uk/beastie_zone.htmI don't know why I find those old things so interesting but I just like messing with them (counters/dividers/flip-flops/schmitt trigger inverters are fun). I wish there was a way to buy one of each ever made in a package for a reasonable price but some 7400 series stuff is probably quite obscure these days.I guess it wouldn't cost too much to get everything here just for funhttp://www.futurlec.com/IC74HC00Series.shtml

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 13, 2016, 12:04:49 am
content: Quote from: mikerj on January 12, 2016, 05:02:50 pmI'm using a value of 150R as I will be driving PC817 optocouplers. I was hoping I could reduce the gate/optocoupler side's quiescent current to <1-2mA (even better if, and I quote from eevblog:"...micro...femto...pico... amps") as it will eventually be run off coin cells if I can.

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 13, 2016, 12:09:16 am
content: Quote from: Kjelt on January 12, 2016, 04:58:21 pmNoooooooooo... No SMDs for me here. Not until I can seriously brush up my soldering skills and have the capability to spin PCBs on my own (it will take a while).Where I live, ferric chloride, HCl H2SO4 etc all require expensive permits to use/store. I'm testing out using vinegar & 3%v/v H2O2 as an etching agent as that's about the only chemicals I can procure freely.

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 13, 2016, 12:20:56 am
content: Quote from: rrinker on January 12, 2016, 04:47:50 pmQuote from: Kleinstein on January 12, 2016, 05:01:24 pmQuote from: dentaku on January 12, 2016, 09:26:11 pmThe 74HCx series sure looks interesting. Prior to this, I honestly didn't realise the 7000 series is a lot more than the 595 shift register....Unlike PICking for PICs; where everything's samey..

author: rrinker
author_rank: Super Contributor
timestamp: January 13, 2016, 01:02:03 am
content: Oh I knew there was a whole series - and all the other variants over the years, like 74S, 74LS, etc. There was a time when I knew all of the common 74 series gates - some of those oddball flip flops and stuff I might have to look up but it I wanted a NAND or OR or inverter, etc. I knew exactly which one that was. Same with the 4000 series. Ah the joys of getting old. And not working with this stuff for a few years.

author: Audioguru
author_rank: Super Contributor
timestamp: January 13, 2016, 01:05:41 am
content: The datasheet for the old Japanese PC817 says it is spec'd with an LED current of only 5mA. Why are you trying to wreck it by blasting in its absolute maximum allowed current of 50mA?

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 13, 2016, 01:13:05 am
content: Quote from: Audioguru on January 13, 2016, 01:05:41 amI was designing the schematic based on Farnell's datasheet:http://www.farnell.com/datasheets/73758.pdfAiming for a Vf of 1.4V, If of 20mA from a constant 5V supply. I got ~150R from calculations.

author: Audioguru
author_rank: Super Contributor
timestamp: January 13, 2016, 01:55:07 am
content: The Sharp datasheet shows a typical Vf of 1.2V (not 1.4V which is max for some of them) when the LED current is 20mA. Then the R should be (5V - 1.2V)/20mA= 190 ohms, not 150 ohms.It is not the 50mA that you said but it is still very high. Why is the current so high?

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 13, 2016, 04:29:06 am
content: Quote from: Audioguru on January 13, 2016, 01:55:07 amI got a derived resistance (Vf = 1.4V which is the max comfortable Vf for the optocoupler according to the datasheet) of 180R, then I decided to round down to the nearest available resistor I currently have as I was thinking of allowing the full circuit (that is using the optocoupler) to be able to milk coin cells as dry as possible. It is still in the extremely early planning stage, so I may either drive it with regulated 5v or 2x coin cells.The optocouplers would probably be turned on (worst case) for ~50-200ms every few mins so I doubt it'd fail that quick...

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 13, 2016, 04:31:14 am
content: Quote from: blueskull on January 13, 2016, 02:17:00 amI think at this point FPGAs are waaaaaay overkill for what I need right now... Not to mention QFN packages......

author: Zero999
author_rank: Super Contributor
timestamp: January 13, 2016, 09:01:53 am
content: Quote from: thejoggingmat on January 13, 2016, 12:09:16 amCan you get sodium persulfate or ammonium persulfate? They're good for etching PCBs and can often be found in some beeches and pool chemicals.SMT adaptor boards can be purchased for prototyping with SMT components. Failing that, you can glue the parts to the board and connect to the pins with enamelled copper wire.As far as logic is concerned. Different families have their advantages/disadvantages.The CMOS CD4000 series has the widest supply voltage range: 3V to 18V but it's slow. The HEF variant is slightly faster but isn't rated to more than 15V. If your find you keep needing single logic gates, then just get a load of the CD4007 MOSFET array which can be configured to perform a variety of functions.The 74HC is faster and is rated from 2 to 6V. The 74HCT variant is only suitable for 5V operation but is compatible with TTL levels and is handy for shifting 3V logic levels to 5V.Old TTL such as 74 and 74LS is obsolete, except for the type with open collector outputs which can be tied via a pull up resistor to up to 30V, so can be used to interface 3V to 5V logic with 12V and 24V automotive/industrial controls.Then there are the faster CMOS families such as 74AC but they can misbehave unless you're careful with the layout and have nice square logic pulses.

author: Audioguru
author_rank: Super Contributor
timestamp: January 13, 2016, 04:36:46 pm
content: Coin cells have a high internal resistance. Then with no load they measure a little higher than 3V but with a load of not many mA their voltage drops quite a lot.

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 14, 2016, 12:16:34 am
content: Quote from: Audioguru on January 13, 2016, 04:36:46 pmThat's what I'm kind of banking on when choosing that low value resistor.Although the side effect will be the transistor constantly saps a lot of quiescent current. So my best bet for that particular circuit would be to find a logic inverter that saps a very low quiescent current.

author: Audioguru
author_rank: Super Contributor
timestamp: January 14, 2016, 03:26:03 am
content: When the transistor is turned off then it uses no current.