Author Topic: Buying components early on.  (Read 5170 times)

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Online bd139

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Re: Buying components early on.
« Reply #50 on: November 13, 2017, 03:00:36 pm »
TTL Cookbook by Don Lancaster is the goto book for this stuff. There's a ton of databooks available but they're all rather large and unwieldy.

You can make any gate with NAND gates :)
 

Offline paulca

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Re: Buying components early on.
« Reply #51 on: November 13, 2017, 03:27:59 pm »
You can make any gate with NAND gates :)

Yes, but you can also slide down a concrete slope in your underpants.  It's entirely possible but not very comfortable :)

In a Computing HNC I did we had to power a single 7 segment display from a 4 bit number using only NAND gates.  I think it ended up with 30 or 40 gates.  (I prefer  Ben Eater's approach of using an EPROM lookup table)
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Offline trys

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Re: Buying components early on.
« Reply #52 on: November 13, 2017, 04:40:41 pm »
In a ScienceFair (Intertan / Tandy / Radio Shack) "300 in One" Electronic Project Lab it comes with the following Digital ICs:

QUAD 2 Input NAND GATE 4011 (2 off)
QUAD 2 Input NOR GATE 4001 (2 off)
4 BIT PRESETTABLE UP-DOWN COUNTER 4029
BCD to 7 SEGMENT DECODER 4511
J-K FLIP FLOP 4027

(It also comes with a bunch of other compoents too, but as you were asking which series of logic ICs to perhaps get I thought I'd type this up, in case it helps).

Edited to add: They are all in stock at CPC as I type this, and the above bunch would come to £3.06 (incl VAT)

Trys
« Last Edit: November 13, 2017, 04:46:48 pm by trys »
 

Offline paulca

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Re: Buying components early on.
« Reply #53 on: November 13, 2017, 04:45:30 pm »
I found this list of the 7400 series: https://en.wikipedia.org/wiki/List_of_7400_series_integrated_circuits

But I am wondering if some of these are more suitable in other series.
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Offline trys

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Re: Buying components early on.
« Reply #54 on: November 13, 2017, 04:53:22 pm »
« Last Edit: November 13, 2017, 04:54:55 pm by trys »
 

Online bd139

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Re: Buying components early on.
« Reply #55 on: November 13, 2017, 05:12:50 pm »
4000 series is mostly pretty dead now apart from a few parts.  There are 74HC series which have replaced it basically. You can get 74HC4xxx series which are much faster ICs compared to their original 4000 counterparts.

Also 74HC are quite fragile static-wise.
 

Offline trys

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Re: Buying components early on.
« Reply #56 on: November 13, 2017, 06:25:11 pm »
The 4000 series are easier to work with as far as supply voltages go.

As far as them being pretty much dead, well yes you are right, and so are the 74 series or discreet logic chips generally. Broadly speaking. Which one is deader than the other is a bit immaterial really. Microcontrollers have taken care of that in the main (yes, I'm aware of lots of exceptions!).

As I said, the 4000 series are available at CPC (as are the 74 series too).

As far as cutting your teeth on logic circuits, then just take your pick.

 

Offline paulca

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Re: Buying components early on.
« Reply #57 on: November 15, 2017, 08:15:54 pm »
So I got my NOR gates (SN74HC02 quad NOR gate)  and wired up an SR Latch.  It works, but, it's a bit of a faff.

I had mind to check the datasheet before I hung LEDs on the outputs and they claim to only provide a max of 25mA current with a max across the chip of 50mA.

I don't have a datasheet for my LEDs, but I'm sure they are 20-30mA.

So I created single NPN drivers for them, but of course to prevent the NPN drawing current through the base I needed resistors between the logic outputs and the base.

It works, but... surely it's a bit of faff having to use transistors to drive the LEDs.  Also the inputs all needed pulled down with resistors or the gates wouldn't function.

I have watched all of Ben Eaters 8-bit computer videos and he typically hangs 8 or more LEDs off a logic circuit.

Am I being overly pedantic and it would probably be fine driving a few LEDs or is Ben Eater risking burning out his logic gates?  Am I reading the data sheet wrong?  Have I got highly sensitive gates? 
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Offline paulca

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Re: Buying components early on.
« Reply #58 on: November 15, 2017, 08:18:49 pm »
Also on buying stuff...  I decided to get a bench power supply and got the Tenma 30V 5A model, it's cheap, but I've seen a few torture and tear down reviews and it seems to be worth the money.

It's a bit noisy when I put it under some load charging a 3S LiPo at 5A, and the fan is still considerably audible on minimum.  Someday I'm probably like to mod it to turn the fan off under 1A.
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Offline trys

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Re: Buying components early on.
« Reply #59 on: November 16, 2017, 02:03:54 pm »
It works, but... surely it's a bit of faff having to use transistors to drive the LEDs.  Also the inputs all needed pulled down with resistors or the gates wouldn't function.

Good on ya for persevering with that despite it being a right faff.

You will probably find that your LEDs will light with just 1mA, so you're looking at a series resistor of 4K7 (or something like that) if the outputs are at 5V. They won't be bright, but you'll be able to see them.

The mA draw of LEDs is usually quoted as maximums to stop us lot frying them. An LED fed with 20mA gives a good bright light.

Trys
 

Online bd139

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Re: Buying components early on.
« Reply #60 on: November 16, 2017, 02:16:00 pm »
Actually if you build yourself a current source as a project, you can see what colours red LEDs go above 20mA or so. It's quite interesting. Wear safety goggles though as the no brand chinese ones tend to explode.
 

Offline paulca

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Re: Buying components early on.
« Reply #61 on: November 16, 2017, 03:50:54 pm »
Actually if you build yourself a current source as a project, you can see what colours red LEDs go above 20mA or so. It's quite interesting. Wear safety goggles though as the no brand chinese ones tend to explode.

I found out that a unlimited green LED turns Amber before the Raspberry PI it's connected to dies when it's cobbler is wired backwards.  Thankfully it wasn't my PI, it was a work owned one.  The LED didn't light when connected sensibly, so bring a little flippant I stuck it across the +- rail of the breadboard.  It went bright amber, then dimmed and the PI went off with the LED.  Neither worked again.

I never did check to see what I pulled the current through or into when the cobbler header was wired backwards.  Something that didn't like killing an LED, I suspect.

On torturing LEDs, I think the Tenma PSU will do 10mA increments, actually think will let me set 1mA increments, but the spec says 10mA resolution (I believe).  That should be enough to destroy an LED or two.  Don't have safety glasses though, but I can use a plastic screen.
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Offline StillTrying

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Re: Buying components early on.
« Reply #62 on: November 16, 2017, 03:57:23 pm »
you can see what colours red LEDs go above 20mA or so. It's quite interesting. Wear safety goggles though as the no brand chinese ones tend to explode.

It must be the heat, in my light experiments, for 10us/4ms I've had 600mA through a 5mm 20mA red LED, and didn't see any colour change.
CML+  That took much longer than I thought it would.
 

Online bd139

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Re: Buying components early on.
« Reply #63 on: November 16, 2017, 04:24:56 pm »
The ones I tried were a bag of 250 of them from Rapid Electronics circa 1995. We connected them to a relatively hefty HP supply with CC support and cranked them up to about 80-100mA. Bright orange following by a radiant shade of black :D

More recently, these ones go with a satisfying snap, especially the blue ones. I bought a whole bag just to blow up: https://www.aliexpress.com/item/500pcs-lot-F5-10-Colors-5MM-Round-Green-Yellow-Blue-White-Red-Warm-White-Orange-Purple/32597550934.html
 

Offline TheDane

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Re: Buying components early on.
« Reply #64 on: November 16, 2017, 04:29:18 pm »
A bit of caution regarding blowing up LED's:

Some components contains poisonous chemicals, and most LED's contain Gallium arsenide.
https://en.wikipedia.org/wiki/Gallium_arsenide - which is rated

High frequency transmitter amplifiers can contain large amounts, and if they blow - the magic smoke can kill quickly - be well..... get outside a.s.a.p. and don't breathe in on the way. Ventilate - Wear a respirator, be safe.
I know, one LED - small. 100kW solid state amplifier - huge.

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Offline paulca

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Re: Buying components early on.
« Reply #65 on: November 16, 2017, 04:56:04 pm »
Some components contains poisonous chemicals, and most LED's contain Gallium arsenide.
https://en.wikipedia.org/wiki/Gallium_arsenide - which is rated

Yes, but you need to eat a plate of the stuff to have a 50% chance of death:

https://wcam.engr.wisc.edu/Public/Safety/MSDS/Gallium%20Arsenide.pdf

Quote
Toxicological impact on health:
Gallium arsenide is considered as acutely non-toxic.
 Animal tox. (for GaAs):
 LD50 (mouse) = 4,700 mg/kg (intraperitoneal)
 LD30 (rat) = 10 g/kg (intraperitoneal)
 LD50 (rat) = 10 g/kg (oral, dermatological)
 That means:
 Classification criteria for hazardous substances do not apply. There is no evidence that inhalation,
ingestion of or skin contact with gallium arsenide (compound semiconductor) has an acute
toxicological impact on health.

So if I weigh 100Kg (I don't), I would need to eat/inhale/drink 470g of the stuff to have a 50% chance of fatal dose.  As a gas at STP that would be many, many litres of pure magic smoke.  There are probably worse things in magic smoke than that.  So I don't recommend putting transistors in a bong.

It's interesting that the Wiki article flags it as Toxic, but then links to a safety data sheet which disagrees.
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Online bd139

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Re: Buying components early on.
« Reply #66 on: November 16, 2017, 05:38:09 pm »
Big ass transmitters are usually full of mercury and beryllium oxide which is where the problems are.
 

Offline paulca

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Re: Buying components early on.
« Reply #67 on: November 16, 2017, 09:21:39 pm »
So update on the 555 project.  It's now gone from 2 breadboards and 19 transistors + 1 test breadboard to 1 small breadboard and a test breadboard.

2xOpAmp comparators and 2xNOR gates on one IC + output and discharge drivers.  Haven't wired the reset, but I'm 50/50 that I just need to jump one of the latch outputs Q or !Q to the reset pin via a trannie to do that.

It works and is a LOT mores stable than the trannie version.

I could go one more step and replace the opamps with actual comparators, but meh.

I'll collect the images I have and make a summary post soon.  It might help another newbie who fancies doing similar.
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Offline trys

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Re: Buying components early on.
« Reply #68 on: November 16, 2017, 10:25:53 pm »
 
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