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> It's more about the relay's coil being an inductor.
This was exactly the point I was trying to make, that wiring up a relay
would "seem" to work (assuming your IC could source enough current) but then
in reality it's going to blow the IC :-D
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Mike Raiford wrote:
> It's more about the relay's coil being an inductor. Once the IC
> switches, it will send a high voltage pulse back through the IC, frying
> it nicely. There are ways to get around that, but I'll leave that as an
> exercise to the reader to figure that out.
More importantly, if the *whole* circuit is relays, there's nothing to
fry. ;-)
(Other than your electricity bill, anyway...)
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> Sure. But I'll bet it isn't a general-purpose logic gate. It'll be some
> special driver IC or something.
Of course, same as your hex buffer you mentioned. But you still can't
connect a relay directly to it without risking damage to the IC (as Mike
explained).
> OOC, what's your hourly rate?
How much you got?
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>> Sure. But I'll bet it isn't a general-purpose logic gate. It'll be
>> some special driver IC or something.
>
> Of course, same as your hex buffer you mentioned. But you still can't
> connect a relay directly to it without risking damage to the IC (as Mike
> explained).
And I still wouldn't try it in the first place. ;-)
>> OOC, what's your hourly rate?
>
> How much you got?
I think we can take it as read that it's peanuts compared to what you
usually make. ;-)
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>>> OOC, what's your hourly rate?
>>
>> How much you got?
>
> I think we can take it as read that it's peanuts compared to what you
> usually make. ;-)
So? Depends how fun it is. If you wanted me to test drive Ferraris then
you needn't pay me very much :-)
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On 25/05/2010 1:07 PM, Mike Raiford wrote:
> It's more about the relay's coil being an inductor. Once the IC
> switches, it will send a high voltage pulse back through the IC, frying
> it nicely. There are ways to get around that, but I'll leave that as an
> exercise to the reader to figure that out.
As Scott said, if you knew more about electronics then you would know
that a back emf diode is an integral part of these circuits and relays
used in process control come with the diodes fitted.
--
Best Regards,
Stephen
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Invisible wrote:
> those tiny 1-hole
> wide wire loops are excruciatingly hard to manipulate.
Needle-nose pliers.
And I don't think you're supposed to use that wire for the battery.
--
Darren New, San Diego CA, USA (PST)
Ada - the programming language trying to avoid
you literally shooting yourself in the foot.
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On 5/25/2010 2:55 AM, Invisible wrote:
> Darren New wrote:
>
>> http://www.robotroom.com/Pumpkin/LEDPulsingBreadboard.jpg
>>
>> See how the black cable goes from C1 to C2?
>>
>> Or how the purple cable goes "around the corner"?
>
> I see...
>
> Makes it kinda hard to rest the ends of the wires on both battery
> terminals simultaneously when they're utterly rigid though. Similarly,
Seriously, go down to the local electronics supply store and buy a
packet of 9-volt battery clips. It makes life much easier!
--
~Mike
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On 5/25/2010 7:08 AM, Invisible wrote:
> I guess it's the way most books refer to circuits as "on" or "off".
> Usually if something is "on" it means it's connected to a power source,
> and if it's "off" then it isn't connected. That's how, e.g., a light
> switch works. It doesn't connect the output to the other pole when you
> turn it off, it just doesn't connect it to *anything*.
Strange... Here's how my mind worked when I encountered the floating
gate = high issue, and not truly realizing logic zero really needs to be
tied to ground:
First I checked the data sheet, and found the information that a
floating input would be interpreted as high. Then I stared at my dip
switch and lamented the fact that it wasn't a SPDT switch. The I
searched the electronics websites for SPDT dip switches, and came up
frustratingly empty. Then started thinking to myself, "How can I make
this work if I only have a SPDT switch" after staring at the circuit I
thought to myself, well, if I connect it to ground with a suitable
resistor, then that should allow the chip to see ground without dumping
tons of current through the switch when its in the on position.
I tried it, and with some trepidation flipped the tiny switch to the on
position and ... it worked just as it was supposed to!
Then I go an research after the fact, playing with the circuit
simulator, and prodding various things in it to find out that yes,
indeed, it does do what I thought it would do. and it makes sense. With
no current from the positive rail, the gate's input can source to
ground. While a voltage is on the positive rail, the gate sinks some of
the current. Exactly what I needed.
A bit more research later and I discovered if I had read a tutorial on
working with logic gates, I would have known about this solution, and
it's called a pull-down or pull-up resistor, depending on which rail it
hooks to.
:)
--
~Mike
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Mike Raiford wrote:
> f I had read a tutorial on working with logic gates,
Heck, if you've ever used a SCSI device you know *that* much. :-)
--
Darren New, San Diego CA, USA (PST)
Ada - the programming language trying to avoid
you literally shooting yourself in the foot.
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