My original LED and Relay question

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".
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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..
--
Sue




Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Peter wrote:

?
http://www.kpsec.freeuk.com/components/tran.htm
Nope, it's two diodes. But it isn't two independent diodes, as lots of diagrams show it.

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..
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Are you the goatse man ?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.