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Home > Archive > Electrical Engineering > May 2007 > My original LED and Relay question
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My original LED and Relay question
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| For anyone who tried helping me, you wasted your time.
I found out what my problem is - I don't know how to read a transistor data
sheet and understand which leg is which.
I assumed the picture was showing the pin diagram from the top of the
transistor (with the legs on the bottom of the transistor), however, it was
showing it with the legs facing up.
Another words: my transistor is in backwards.
After doing all this research as to why my relay wouldn't work, I came
across two specs I don't understand for the DSP1-DC5V.
It states a pick-up voltage of 4 volts (max) and a drop out voltage of 0.5
volts (min).
To me, that states the relay needs a maximum of 4 volts to turn on and will
remain on until reduced to 0.5 volts. If it's a 5 volt relay, then the 4
volts should state "minimum".
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| Palindrome 2007-05-17, 8:25 pm |
| Peter wrote:
> For anyone who tried helping me, you wasted your time.
>
> I found out what my problem is - I don't know how to read a transistor data
> sheet and understand which leg is which.
>
> I assumed the picture was showing the pin diagram from the top of the
> transistor (with the legs on the bottom of the transistor), however, it was
> showing it with the legs facing up.
>
>
> Another words: my transistor is in backwards.
Someone suggested that you had reversed c and e, IIRC.
>
>
> After doing all this research as to why my relay wouldn't work, I came
> across two specs I don't understand for the DSP1-DC5V.
>
> It states a pick-up voltage of 4 volts (max) and a drop out voltage of 0.5
> volts (min).
>
>
> To me, that states the relay needs a maximum of 4 volts to turn on and will
> remain on until reduced to 0.5 volts. If it's a 5 volt relay, then the 4
> volts should state "minimum".
If you apply an increasing voltage to the relay coil, the maximum
voltage that you need to apply to ensure that the relay is turned on is
4 volts. The minimum voltage that can cause one of these relays to turn
on will be somewhat less..
--
Sue
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| Palindrome <me9@privacy.net> wrote in
news:U853i.54128$MW1.29407@fe03.news.easynews.com:
> Peter wrote:
>
> Someone suggested that you had reversed c and e, IIRC.
>
>
> If you apply an increasing voltage to the relay coil, the maximum
> voltage that you need to apply to ensure that the relay is turned on
> is 4 volts. The minimum voltage that can cause one of these relays to
> turn on will be somewhat less..
>
Well I measured the Vbe and had 0.7 volts and triple checked the
drawing. But you're correct, someone suggested it and it was the
problem.
I've never understood the concept of a transistor being x2 diodes. The
base to emitter diode is understandable, but the collector "diode" has
its anode on the base and the cathode on the collector.
Is it theoreticaly a zener diode then? I always assumed the collector
diode faced into the base, however, that's not the case.
About the relay spec. I would think they'd spec it as: Minimum pick-up
voltage (or turn on voltage) is X volts. This way I know if I apply X
volts to its max, it will turn on.
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| Palindrome 2007-05-17, 8:25 pm |
| Peter wrote:
> Palindrome <me9@privacy.net> wrote in
> news:U853i.54128$MW1.29407@fe03.news.easynews.com:
>
>
>
>
> Well I measured the Vbe and had 0.7 volts and triple checked the
> drawing. But you're correct, someone suggested it and it was the
> problem.
>
> I've never understood the concept of a transistor being x2 diodes. The
> base to emitter diode is understandable, but the collector "diode" has
> its anode on the base and the cathode on the collector.
?
http://www.kpsec.freeuk.com/components/tran.htm
>
> Is it theoreticaly a zener diode then? I always assumed the collector
> diode faced into the base, however, that's not the case.
Nope, it's two diodes. But it isn't two independent diodes, as lots of
diagrams show it.
>
> About the relay spec. I would think they'd spec it as: Minimum pick-up
> voltage (or turn on voltage) is X volts. This way I know if I apply X
> volts to its max, it will turn on.
>
>
That would mean that you need 4 volts, as a minimum, to operate the
relay. Which is untrue - many of these relays will pull in at less than
that. The minimum turn on voltage is possibly going to be around
3.4volts.. But the maximum you need to operate the relay is 4 volts..
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| Rubber Glover 2007-05-18, 1:25 pm |
|
"Peter" <private@private.com> wrote in message
news:so-dne0HB44SR9HbnZ2dnUVZ_v6tnZ2d@comcast.com...
> For anyone who tried helping me, you wasted your time.
>
> I found out what my problem is - I don't know how to read a transistor
> data
> sheet and understand which leg is which.
>
> I assumed the picture was showing the pin diagram from the top of the
> transistor (with the legs on the bottom of the transistor), however, it
> was
> showing it with the legs facing up.
>
>
> Another words: my transistor is in backwards.
>
>
> After doing all this research as to why my relay wouldn't work, I came
> across two specs I don't understand for the DSP1-DC5V.
>
> It states a pick-up voltage of 4 volts (max) and a drop out voltage of 0.5
> volts (min).
>
>
> To me, that states the relay needs a maximum of 4 volts to turn on and
> will
> remain on until reduced to 0.5 volts. If it's a 5 volt relay, then the 4
> volts should state "minimum".
Are you the goatse man ?
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| gfretwell@aol.com 2007-05-18, 1:25 pm |
| On Thu, 17 May 2007 17:43:27 -0500, Peter <private@private.com> wrote:
>For anyone who tried helping me, you wasted your time.
>
>I found out what my problem is - I don't know how to read a transistor data
>sheet and understand which leg is which.
>
>I assumed the picture was showing the pin diagram from the top of the
>transistor (with the legs on the bottom of the transistor), however, it was
>showing it with the legs facing up.
>
>
>Another words: my transistor is in backwards.
>
>
>After doing all this research as to why my relay wouldn't work, I came
>across two specs I don't understand for the DSP1-DC5V.
>
>It states a pick-up voltage of 4 volts (max) and a drop out voltage of 0.5
>volts (min).
>
>
>To me, that states the relay needs a maximum of 4 volts to turn on and will
>remain on until reduced to 0.5 volts. If it's a 5 volt relay, then the 4
>volts should state "minimum".
I got some generic 2n2222s that were clearly wired wrong (collector
and emitter swapped), and I used some other, known good, ones to prove
my point. I had similar problems but I thought it was just an isolated
thing.
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