relay coils and transistors ( again )

Archiver

I had previously asked general questions about relays and transistors,· I would· now like to specify· that· I am· working with a· S101505V· Sharp Relay· that is solid state, and is 5V+ and carries a load of 125 VAC...it was purchased at RShack and its part # there is 275-310. Has anyone used this relay?· I have been trying to incorporate it into a project but have not yet successfully switched a load with· it· yet.· Tested relay·by applying 5V to the contacts and checking for continuity on the load contacts.....got· nothing, so I assumed· I· had a bad relay,· but· now· I get the· same· out· of· a· replacement...any· suggestions?· here is a link to the project· Im patterning· mine· after.....· http://geocities.com/SiliconValley/Orchard/6633/vbonoff.html

Also, instead of a 2N2222 NPN type transistor,· I have used a MPS2222A· ( Rshack # 276-2009 )· Is this a red flag to anyone? Finally, the 10k resistor is a 1/2 watt instead of a 1/4,· I have been told· that· this· will still work?
·I have previously built the··LED test circuit and that worked fine, so I am puzzled where the· problem lies....thanks in advance.

Dave
·

Archiver

Hi Sam

If I'm not mistaken, that SSR (solid state relay) is triac-based, so it only
switches AC power. That means that an ohm meter will never show it "close".

There is no "coil" per se, so you shouldn't need any protection diodes. Some
of these draw a small amount of current (a dozen mA or so) and you could
probably drive them right from a Stamp pin. Also, the "coil" on these units
may well be polarized -- The - terminal goes to ground and the + terminal
goes to the switching voltage (1.2V will make it switch).

Your transistor should be OK. With the emitter grounded, the base will be at
about .6V. If you put 5V on the other side of the 10k resistor, you'll
develop a base current of (5-.6)/10000 = 440uA. The transistor has a high
gain, so that will likely saturate the transistor and the voltage at the
collector will be about .2 or .3V. Even if it operates linear with a beta of
100, Ic would be 44mA. If you replace the relay with a 330 ohm resistor
(about 15mA at 5V) you should be able to see the collector voltage go from
5V to .2 or .3V when you change the Stamp output. If you don't, then I'd
imagine you have the transistor EBC leads misidentified. Of course, like I
said, the Stamp outputs are relatively beefy so you might be able to drive
it directly.

Hope that helps.

Al Williams
AWC
*Floating point math for the Stamp, PIC, SX, or any microcontroller:
http://www.al-williams.com/awce/pak1.htm

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Original Message

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From: samhell@s... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=mPpBk1BfO4LAuXIweuXqxN1jJMnFy1aM9lkOPUUbjec-HCT5pZfTvac3JXmjO59Yv0FB7aqpi97Y]samhell@s...[/url
Sent: Tuesday, September 05, 2000 12:14 AM
To: basicstamps@egroups.com
Subject: [noparse][[/noparse]basicstamps] relay coils and transistors ( again )


I had previously asked general questions about relays and transistors, I
would now like to specify that I am working with a S101505V Sharp
Relay that is solid state, and is 5V+ and carries a load of 125 VAC...it
was purchased at RShack and its part # there is 275-310. Has anyone used
this relay? I have been trying to incorporate it into a project but have
not yet successfully switched a load with it yet. Tested relay by
applying 5V to the contacts and checking for continuity on the load
contacts.....got nothing, so I assumed I had a bad relay, but now I
get the same out of a replacement...any suggestions? here is a link
to the project Im patterning mine after.....
http://geocities.com/SiliconValley/Orchard/6633/vbonoff.html

Also, instead of a 2N2222 NPN type transistor, I have used a MPS2222A (
Rshack # 276-2009 ) Is this a red flag to anyone? Finally, the 10k resistor
is a 1/2 watt instead of a 1/4, I have been told that this will still
work?
I have previously built the LED test circuit and that worked fine, so I am
puzzled where the problem lies....thanks in advance.

Dave

Archiver

samhell@s... writes:

>I am working with a S101505V Sharp Relay that is solid state, and is
5V+ and carries a load of 125 VAC...<<<snip>>>

>Tested relay by applying 5V to the contacts and checking for continuity on
the load contacts.....got nothing, so I assumed I had a bad relay,
<<<snip>>>


You can't check a solid state relay by testing for resistance. It doesn't
work that way. You need you try switching an AC load, like a light bulb.

<

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110-125 VAC |
<

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[noparse][[/noparse]o o]

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[noparse][[/noparse]Light Bulb]---|
[noparse][[/noparse] AC AC]
/ [noparse][[/noparse] SSR ]
+5V---/

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[noparse][[/noparse]o+ -o]

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|
switch |
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///
Hope this helps,

Steve

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Steve Roberts: sroberts@s...

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