Electromechanical relay switching frequency

[bluedot]

Hello everybody,

 

I'm looking for an electromechanical relay capable of high switching rate (make and break) up to 100 Hz.

Relay is supposed to be for 24 V DC circuit and of small curent rating (100-200 mA).

I know such a high switching rate is difficult demand for electromechanical relays, and manufacturers I contacted told me they don't have anything above 20 Hz. However, I researched myself and found in the book "Electromechanical systems in Microtechnology and Mechanotronics" the following table:

Therefore, the relays I'm looking for certainly exist, but I don't know where they are used .

Anybody here know something about such relays and where I can get them?

Thanks

[imatfaal]

Being dense here - but if a 1 cycle is, say, on...bounce...off... then with half a millisecond for each (per your table) then the highest rate you could get would be 666 hertz.

 

But really not my scene so maybe I have definitions wrong and maybe you need two bounces

Edited April 15, 2015 by imatfaal
micro to milli

[studiot]

Relays are usually specified by switching time.

 

Cheap relays offer something like 5 - 15 millisecond times.

 

You have the following sum

 

Switch on time + on time + switch off time + off time = time for one cycle = period.

 

With 5 milliseconds each you have

 

Period = 5+5+5+5 = 20 milliseconds.

 

This translates to a frequency of 50 cycles/second.

 

As regards current, this only flows during the on time so in the example the duty cycle is 5/20 = 0.25.

 

The average current = current during one time x duty cycle.

 

The on current is determined by the resistance of the external components.

 

So you are looking for a 24volt relay with better than 5ms switching time.

 

CPC offer some cheap ones at 8ms

 

But they have several hundred in their catalog so try their technical helpline.

[Externet]

Hi.

Your emphasis in electromechanical (not same as electromagnetic) led me to question if piezoelectric relays exist. Seems yes. Or make-design your own.

Check U.S. patent 3,430,020. I did not read it all myself.

 

A second way that comes to my mind and may or not fit your needs could be a shallow rotary shaft/cam and contact points as in automotive distributor. Will be also electromechanical.

 

Brushes on a multi segmented rotor is another way you can explore if feel like applicable.

 

[Trying to respect your guideline on not using very low resistance mosfets as the modern industry standard switching method]

Edited April 15, 2015 by Externet

[studiot]

Reed relays get you down to 0.5ms switching time which make kHz frequencies quite feasible.

 

CPC offer reeds with amps capability.

[bluedot]

Reed relays get you down to 0.5ms switching time which make kHz frequencies quite feasible.

 

CPC offer reeds with amps capability.

Can you give a link to the techical data/catalogue of one of these please?

Also, there is something else I'm puzzled with.

Consider data CPC gives for this one:

http://cpc.farnell.com/te-connectivity-schrack/sr4m4024/relay-forced-contact-24vdc/dp/SW03967

They state an operating time 12ms and release time 20 ms.

My question is what is max switching frequency for this relay?

[studiot]

It depends upon the current drawn.

 

Frequency is not an appropriate parameter to be using

 

Did you not manage to follow my post #3 ?

 

What needs explaining further?

 

 

http://www.farnell.com/datasheets/1884830.pdf

Edited April 15, 2015 by studiot

[bluedot]

It depends upon the current drawn.

 

Frequency is not an appropriate parameter to be using

 

Did you not manage to follow my post #3 ?

 

What needs explaining further?

 

 

http://www.farnell.com/datasheets/1884830.pdf

This looks like a solid state device with bunch of electronic components. I don't like it.

Edited April 15, 2015 by bluedot

[studiot]

If you don't want to engage in discussion, why ask the question?

 

I linked to a large matrix switching device, but Farnell sell spare parts, which you require.

 

You didn't respond to a polite offer to discuss a subject in which you are clearly non expert and I thought were seeking help.

 

Sorry I wasted my time and effort.

[bluedot]

It depends upon the current drawn.

 

Frequency is not an appropriate parameter to be using

 

It depends on electric and mechanical "inertia" of the relay system (assuming the relay is properly used within rating range).

As always, knowing some of the terminology is helpful. I didn't know what exactly mean the operating time and the release time of the relay but I found out.

Operating time = the time interval from the initial application of power to the relay coil until the closure of the normally open contacts.

Release time = the time interval from the relay coil de-energization until re-closure of the normally closed contacts.

So for the relay in post #6 data indicate the period of 1 cycle : 12 + 20 = 32 ms (at least)

At least because operating and release times exclude bounce time of the contacts ( possibly it may contribute with few ms there).

I conclude that this relay has max switching frequency below 30 Hz.

 

Now, what cheap relay with times 8 ms you mention in post #3 you refered to?

That one sounds promising for 50 Hz mark.

Edited April 15, 2015 by bluedot

[studiot]

Is it my aftershave or what?

 

I offer you a formula containing all the variables inherent in determining cycle time

 

The response is total silence.

 

I tell you that cycle can be asymmetric and that the current you can draw depends partly on one of the variables in my first equation.

 

Again total silence.

 

I find you a fast switching relay (the fastest type available)

 

And you are rude about it.

 

I can't see why you persist with your post#6 relay, it is clearly not suitable for your needs.

[bluedot]

Well, it was you who informed CPC offer cheap el-mech relays with 8 ms switching times. You didn't point to any link or catalogue of such. So, I went to their sales page and didn't find any such (perhaps, there is but I can't find it). Only cheap relays with times like linked in post #6. Then I asked about max switching frequency of that relay wondering about meaning of terminology in data sheet. I got indefinite answer, while answer for upper possible frequency is easy to derive from the data. Then you gave me the link to more than fast enough but very "cheap" reed relay components. I asked you again to specify cheap relay with 8 ms switching time you had on mind. Total silence. Thanks for help!

Edited April 16, 2015 by bluedot

[bluedot]

Don't bother. At one German distributer I finally found one small relay with operating time 5 ms and release time 3.5 ms that satisfy my needs.

[studiot]

In the 1950s and 1960s (valve) car radios were operated by vibrator based power supplies that ran continuously at 100 to 200 Hz.

You may like to watch these as they contain much pertinent wisdom, most particularly about the switching voltage spikes.

 

Watch this one first from a service engineer

 

https://www.youtube.com/watch?v=Fp6PkRTmb8U

 

Then this one from a modern experimenter.

 

https://www.youtube.com/watch?v=nHq6vArLVc8

 

There is considerably more circuit theory you need to know to use these things (electromechanical devices) successfully in continuous mode, good luck in your search since you don't want help here.

Edited April 16, 2015 by studiot