So these things all seem to be functionally, and as far as I can tell structurally identical, with the only difference in terminology being related to the amount of current being switched. Is there more to it than that, or does the electrical world just need to pick one damn name.
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Feb. 27, 2011 9:13 p.m. DILYSI Dave SuperDork
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Feb. 27, 2011 9:32 p.m. carzan HalfDork
Well, for one thing, a relay can be solid-state with no mechanical contacts, so they are not necessarily structurally identical.
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Feb. 27, 2011 9:37 p.m. HiTempguy Dork
DILYSI Dave wrote:
Is there more to it than that, or does the electrical world just need to pick one damn name.
There are usually differences... but lots of companies/designers use the words interchangeably, and for anybody that is not an electrician/electrical engineer it doesn't really matter (like a new electrical engineer grilling me on if they are relays or contacts on some PLC equipment I used to sell, fawked if I know, the manufacturer uses the words to mean the same thing!)
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Feb. 27, 2011 9:46 p.m. DILYSI Dave SuperDork
It matters to the part pickers at Autozone. I was wanting a starter relay for a 1985 Ford truck. They swore that no such thing existed. I pulled out a picture I had of one and they said "Oh - you mean a starter solenoid."
I mean the berkeleying thing that you put low current to so that you can switch high current!
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Feb. 27, 2011 10:23 p.m. carzan HalfDork
DILYSI Dave wrote:
Yup, in this app., they're pretty much the same. The solenoid is mounted on the fender of my '87 Ford truck and yes, it's just a relay.It matters to the part pickers at Autozone. I was wanting a starter relay for a 1985 Ford truck. They swore that no such thing existed. I pulled out a picture I had of one and they said "Oh - you mean a starter solenoid."
I mean the berkeleying thing that you put low current to so that you can switch high current!
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Feb. 28, 2011 12:07 a.m. EvanR Reader
A relay is a TYPE of solenoid.
A solenoid converts electricity to mechanical motion.
In a relay, a solenoid converts electricity into mechanical motion. The particular mechanical motion involves closing a set of high-current contacts.
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Feb. 28, 2011 6:43 a.m. carzan HalfDork
EvanR wrote:
A relay is a TYPE of solenoid.
Actually, no. A relay is a relay. A solenoid is a solenoid. A relay is a remotely operated switch. A solenoid is an electromagnetic device that is primarily an actuator. In the case of a Ford truck, the “solenoid” is a relay operated by a solenoid device.
A relay can be operated electromagnetically, pneumatically, hydraulically or electronically (solid state).
A solenoid can operate relays, valves,. and any number of other mechanically operated devices.
Using the term “solenoid” to describe what the OP was referring to is a misnomer as far as I’m concerned, but that is what they’ve been called as long as I can remember.
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Feb. 28, 2011 7:29 a.m. DILYSI Dave SuperDork
Tangent...
What should the low side current draw be on these things? IE, what current do I need to fuse the control circuit to handle?
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Feb. 28, 2011 9:49 a.m. Keith SuperDork
Many cars have both a starter relay and a starter solenoid. Examples: a 1972 MGB GT and a 2000 Toyota Tundra. I'm not sure what else those two vehicles have in common, electrically speaking.
Regardless, when the starter relay went out on my Tundra I assumed anyone who said "relay" was talking about the solenoid. Could have saved myself a lot of work. A failure of one acts a lot like the failure of the other unless you know there's a relay in the system - and to make things more interesting, the starter is under the intake manifold so you can't really check voltage at the solenoid without doing a lot of digging. That was a frustrating day...
Aren't many transistors basically small solid-state relays?
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Feb. 28, 2011 11:11 p.m. DILYSI Dave SuperDork
Well, whatever the hell it's called, it is now installed on my civic, where it is used to switch the electric power steering pump.
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Feb. 28, 2011 11:23 p.m. WilberM3 HalfDork
what electric pump is that?
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Feb. 28, 2011 11:25 p.m. DILYSI Dave SuperDork
MR2.
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March 1, 2011 5:49 a.m. carzan HalfDork
Nice!
The only thing I could find on current draw was a posting on another forum by someone who measured it himself. He says he measured less than 2 amps.
