Help with Schematic Symbol

Sirius

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Could someone tell me what it is that's in the circle of the attached schematic? It's for the POR signal on a space invaders ps.
 

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Yes. And if you're looking for one, you won't find one by itself. They tend to come in six-packs. For example, perhaps one of the most common is the 74LS04, "Hex inverter". The "hex" means there are six seperate inverters on that single (14-pin) chip. So, if you wish to build that circuit, using TTL logic, you'll need a 74LS04 (or similar), and only use one of the six inverters in it.

I suppose you could build you own single inverter with a transistor and a couple of resistors, but that's another topic.

BTW, were'd the diagram come from? Seems like I remember seeing it before, but now I can't find it.

PPS--FWIW, on my test bench (with a switcher) I've had two SI boardsets work just fine with the POR line (on the daughter board) simply tied to ground...
 
Yes. And if you're looking for one, you won't find one by itself. They tend to come in six-packs. For example, perhaps one of the most common is the 74LS04, "Hex inverter". The "hex" means there are six seperate inverters on that single (14-pin) chip. So, if you wish to build that circuit, using TTL logic, you'll need a 74LS04 (or similar), and only use one of the six inverters in it.

I suppose you could build you own single inverter with a transistor and a couple of resistors, but that's another topic.

BTW, were'd the diagram come from? Seems like I remember seeing it before, but now I can't find it.

PPS--FWIW, on my test bench (with a switcher) I've had two SI boardsets work just fine with the POR line (on the daughter board) simply tied to ground...

It comes from the the pin out chart for the 2/3 layer board sets in SI. If I can simply tie it to ground that's what I'll do. I have a SI power supply that keeps blowing the 2 amp fuse and I cant find the bad part on it. I was thinking of just putting in a switcher and call it good.
 
It comes from the the pin out chart for the 2/3 layer board sets in SI.

I think you must be referring to this: http://www.robotron-2084.co.uk/manuals/invaders/taito_space_invader_2+3_layer_board_pinout.pdf

Thanks for helping me remember where I'd seen it.

Anyhow, AFAIK the "component" in that diagram doesn't exist. I'm not familiar with any inverter IC that has power on pin 1, GND on pin 8, and input/output on pins 2 & 3. Maybe there is one... I'd be interested in someone could name it.

If you decide to build that circuit, here's a 7404 (or 74LS04) pinout:
7404.gif


Wire up the +5V to "Vcc", GND to GND, and the input and output any of the 6 inverters, per that diagram you posted (ignoring the little numbers).
 
I'll try tying to ground first and see if that works. I think I have some 74ls04's, so if I need to build it I can. Thanks for the info...
 
i was looking at that diagram, if pins 1/8 were flipped, and 2/3 were flipped it would almost have the pinout of a 555 timer :p

heck, you could flip the resister, and cap, and use an opamp to do the same thing.

bascilly what you have there is a power on reset delay, if the cap is shot, then it will have no delay :) and reset ic could work in its place.

Such as a Dallas DS1811

you could easily mount a DS1811 in the place of that component if it truly is a 8 pin package.
 
I'm probably nitpicking here, but normally, an inverter is drawn as a triangle with a 'hollow' dot at the output end, like in the 7404 diagram above. I'm sure the OP's drawing is for an inverter, but they mistakenly blacked out the dot. A solid black dot just represents a wiring connection, and a plain triangle by itself represents an op amp.
 
I'm probably nitpicking here, but normally, an inverter is drawn as a triangle with a 'hollow' dot at the output end, like in the 7404 diagram above. I'm sure the OP's drawing is for an inverter, but they mistakenly blacked out the dot. A solid black dot just represents a wiring connection, and a plain triangle by itself represents an op amp.


I have seen them drawn about a half dozen different ways, it depends on where the drawing came from. When I am teaching people how to read schematics I actually use six different reference drawings in order to show the students how different companies depicted things differently over the years.
 
i was looking at that diagram, if pins 1/8 were flipped, and 2/3 were flipped it would almost have the pinout of a 555 timer :p

Good idea! According to this page, you'd need to also connect the TRIG line to the input, and tie the RESET line high, to use a 555 as an inverting gate: http://www.kpsec.freeuk.com/555timer.htm#buffer

In fact, that sounds so cool, I may make myself a 555-based power-on reset circuit for my SI test rig, even though I don't really need it :p (as I've never had problems just grounding the reset line)
 
The pinout on that doesn't match an inverter... unless you didn't fill out the power pin designation properly.
 
Ok boys and girls...I got the answer directly from the source

It's a "4049"

Below is his response...

On 29 Jan 2013 10:59pm, Sirius wrote:
> What is the best chip to use for the Space Invaders POR circuit?
>
>

Hmmm .... in 10 years no-one has ever asked that despite the fact it doesn't say on the document!

Anyway, it's a 4049.
 
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