# relay switching speed

Discussion in 'Electronic Basics' started by lerameur, Aug 22, 2008.

1. ### lerameurGuest

hello,

I am trying to figure out is there is any rating on the maximum
switching speed on mechanical relays such as the R3-24AC or 50-094-0
(or just any mechanical relay) I want to use dc current on these and
switch them possibly 1000Hertz or possibly 10,000Hertz. what is the
maximum speed they can be continuously switch?
thanks

K

lerameur, Aug 22, 2008

2. ### Sjouke BurryGuest

lerameur wrote:
> hello,
>
> I am trying to figure out is there is any rating on the maximum
> switching speed on mechanical relays such as the R3-24AC or 50-094-0
> (or just any mechanical relay) I want to use dc current on these and
> switch them possibly 1000Hertz or possibly 10,000Hertz. what is the
> maximum speed they can be continuously switch?
> thanks
>
> K

The "on" switching time is depending on the speed with which
you can push current into the relay coil, and would rather
quickly get into the range to burn out the coil, if you want
high switching speed.
The "off" switching time however depends two things, first how
fast you can kill the current in the relay(rather difficult),
and secondly on a metal spring in the relay to pull the relay "open".

The spring is what is limiting the ultimate speed.

An ordinary relay will be ~50-200 hz, and very small relays, like a
reed relay for example might be pushed a bit higher, like 200-400 hz

A quick test would be to put the NO contact in series with the coil,
and make it self-switching, acting like a buzzer.

You can increase the supply voltage a bit, but you risk burnout of the
coil.
Also the contacts wont last long.

1000Hz? unlikely.
10000hz? wishful thinking.
If you really want fast mechanical switching , use a rotary switch,
driven by a motor.

Using FET switches, you can get into the Megahz range.

Sjouke Burry, Aug 22, 2008

3. ### lerameurGuest

Re: relay switching speed

On Aug 22, 2:14 pm, Sjouke Burry <>
wrote:
> lerameur wrote:
> > hello,

>
> > I am trying to figure out is there is any rating on the maximum
> > switching speed on mechanical relays such as the R3-24AC or 50-094-0
> > (or just any mechanical relay) I want to use dc current on these and
> > switch them possibly 1000Hertz or possibly 10,000Hertz. what is the
> > maximum speed they can be continuously switch?
> > thanks

>
> > K

>
> The "on" switching time is depending on the speed with which
> you can push current into the relay coil, and would rather
> quickly get into the range to burn out the coil, if you want
> high switching speed.
> The "off" switching time however depends two things, first how
> fast you can kill the current in the relay(rather difficult),
> and secondly on a metal spring in the relay to pull the relay "open".
>
> The spring is what is limiting the ultimate speed.
>
> An ordinary relay will be ~50-200 hz, and very small relays, like a
> reed relay for example might be pushed a bit higher, like 200-400 hz
>
> A quick test would be to put the NO contact in series with the coil,
> and make it self-switching, acting like a buzzer.
>
> You can increase the supply voltage a bit, but you risk burnout of the
> coil.
> Also the contacts wont last long.
>
> 1000Hz? unlikely.
> 10000hz? wishful thinking.
> If you really want fast mechanical switching , use a rotary switch,
> driven by a motor.
>
> Using FET switches, you can get into the Megahz range.

Ok I found this part at Digikey.com
CLA280-ND
it is a static relay, that can handle the required switching but it
is not a SPDT, and there are no SPDT in the 6 amps or higher
regions.... are these high power relays done in static technology?

K

lerameur, Aug 22, 2008
4. ### whit3rdGuest

Re: relay switching speed

On Aug 22, 10:46 am, lerameur <> wrote:

> I am trying to figure out is there is any rating on the maximum
> switching speed on mechanical relays ...
> I want to use dc current on these and
> switch them possibly 1000Hertz or possibly 10,000Hertz.

Firstly, if the coil current is modulated at 1000 Hz, this is NOT DC
current
we're talking about. On every cycle, you'll generate some core heat
due to magnetization losses. This may be important. Smoke
is possible. Do not expect that 'normal' operating voltages are
sufficient, either

Secondly, the 'ON' position of the relay is achieved by hitting a pair
of parts together , and they either progress to hammer each other
out of shape OR they engage in elastic deformation. That elasticity
means there is bounce, and the 'ON' status is very much compromised
until the bouncing stops. This is the one, the only, item that a
relay
manufacturer is likely to specify about the short-time character of
the relay.

And third, the 'OFF' position usually is a long way from the 'ON',
so that sparks don't occur. If you expect 5 kV operation, or 50 mV
operation, the suitable delay-to-OFF time will be quite different.
Some small-signal (telephone) relays have impressive contact lifetime
with circa 50V stress; lower voltages have dirt-related reliability
issues, and higher voltages have wrath-of-Zeus related reliability
issues.
At 1 kHz your prospective device will hit millions of times per hour,
and contact life will be a major issue. Practical vibrators (I seem
to recall)
worked at tens of Hz.

The literature on this kind of application is heavily influenced by
Motorola
and relates to early car radios (which Motorola made); the oscillating
'relay' was called a vibrator, and failed as frequently as any of the
vacuum
tubes.

whit3rd, Aug 23, 2008
5. ### JamieGuest

lerameur wrote:
> hello,
>
> I am trying to figure out is there is any rating on the maximum
> switching speed on mechanical relays such as the R3-24AC or 50-094-0
> (or just any mechanical relay) I want to use dc current on these and
> switch them possibly 1000Hertz or possibly 10,000Hertz. what is the
> maximum speed they can be continuously switch?
> thanks
>
> K

Most likely induction is to high in the coil for that kind of speed,
you'll never get enough current to pull the contacts.

Assuming this is a 24 Volt AC coil, it has been wound and designed
to create enough current with in the cycle time of 50/60 hz..

Ect...

http://webpages.charter.net/jamie_5"

Jamie, Aug 23, 2008
6. ### Jasen BettsGuest

On 2008-08-22, lerameur <> wrote:
> hello,
>
> I am trying to figure out is there is any rating on the maximum
> switching speed on mechanical relays such as the R3-24AC or 50-094-0
> (or just any mechanical relay) I want to use dc current on these and
> switch them possibly 1000Hertz or possibly 10,000Hertz. what is the
> maximum speed they can be continuously switch?
> thanks

typical DC relays are good to something around 100Hz
(AC relays have slower switching rates)

you may be able to coax higher rates by closed loop control
ISTR getting about 300Hz in this way once. (i wired the NC contats in
series with the coil and adjusted the supply for the highest pitch)

if you want to go higher you may need to consider piezo actuators
instead of magnetic, or go solid-state instead.

Bye.
Jasen

Jasen Betts, Aug 23, 2008
7. ### kammenos

Joined:
Aug 18, 2008
Messages:
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0
Absolutely imposible. Relays are not to work like this. They are to carry heavy loads. You should consider using some kind of transistor or anything else. What exactly are you trying to make?

kammenos, Aug 23, 2008
8. ### Bob EldGuest

"lerameur" <> wrote in message
news:...
> hello,
>
> I am trying to figure out is there is any rating on the maximum
> switching speed on mechanical relays such as the R3-24AC or 50-094-0
> (or just any mechanical relay) I want to use dc current on these and
> switch them possibly 1000Hertz or possibly 10,000Hertz. what is the
> maximum speed they can be continuously switch?
> thanks
>
> K

Forget about it. As mentioned in all of the above posts, relays are far too
slow for your application. AC relays are even slower because they have a
copper "shade" on the pole piece to deliberately keep the field from
collapsing fast. This keeps the relay from chattering on AC drive.

Your application requires electronic switching for the speeds you mention.
Transistors, FETs, SCRs, etc. should be considered depending on the exact
requirements.

Bob Eld, Aug 23, 2008
9. ### Ross HerbertGuest

Re: relay switching speed

On Fri, 22 Aug 2008 11:44:22 -0700 (PDT), lerameur <> wrote:

:Ok I found this part at Digikey.com
:CLA280-ND
: it is a static relay, that can handle the required switching but it
:is not a SPDT, and there are no SPDT in the 6 amps or higher
:regions.... are these high power relays done in static technology?
:
:K

Did you look at the datasheet?
http://clareweb2.clare.com/home/pdfs.nsf/0/614B59328CA886C28525726600495950/\$file/CPC1709.pdf

Max T-on is 20mS and max T-off is 5mS. This limits the maximum (reliable)
operating speed to 40 operations per second but you would need some safety
margin. Say around 37 ops per second guaranteed.

A reed relay will typically have operate and release time of around 1mS but they
can't handle the current you are talking about.

Ross Herbert, Aug 24, 2008
10. ### Ross HerbertGuest

Re: relay switching speed

On Sun, 24 Aug 2008 07:56:02 GMT, Ross Herbert <> wrote:

id you look at the datasheet?
:http://clareweb2.clare.com/home/pdfs.nsf/0/614B59328CA886C28525726600495950/\$file/CPC1709.pdf
:
:Max T-on is 20mS and max T-off is 5mS. This limits the maximum (reliable)
perating speed to 40 operations per second but you would need some safety
:margin. Say around 37 ops per second guaranteed.
:

And that is assuming that an on time of say 1 - 2mS is sufficient to perform the
required function.

Ross Herbert, Aug 24, 2008
11. ### neon

Joined:
Oct 21, 2006
Messages:
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0
just forget relay for that speed theywere never meant to switch that fast. reeds might do it as mechanical switching but even them are not realibly at that speed . BOTTOM LINE FET or transistors.

neon, Aug 24, 2008

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