relay contact times

[arivel]

Hello . I would like to ask a few questions about DC electromechanical relays. let's consider a quantity of signal relays that are all the same. the relay contacts take a certain time to close and a certain time to switch off. I assume that each relay has slightly different closing and opening times than the others. how much could the difference be in milliseconds?. I don't know yet if it's worth it, because I don't know how much time difference there is between one relay and another, the need is to obtain perfectly synchronized closing and opening of the contacts of all relays. in case you need to turn on and off a small group of relays, say three or five, instead of powering the coils together individually and in parallel at the same voltage is it possible to power the coils in series using a higher total voltage? does this solve the problem?

 

[canadaelk]

Relay data sheets will have a graph, similar to the attachment, giving you the info you need. Relays contacts will chatter (open and close multiple times) until they permanently close after the voltage is applied.
Wiring the relays in series (using the proper voltage) will not change that as it is a mechanical property of the relay. E

 

[MaxHeadRoom78]

Also the common practice of placing BEMF diodes across DC coils causes a delayed drop out situation.
If you need high prescision synchronization, maybe look at a solid state solution.
Max.

 

[arivel]

si riflettendo devo essere d'accordo con te.

 

[eTech]

Series relays will cause more issues and will operate slower. Connect them in parallel and run at a slightly higher voltage than nominal. This will make them faster. Be sure to use a diode around each coil. But a parallel connection will not eliminate contact transfer time manufacturing variances. When it was critical, We actually had an automated test fixture to perform a specification check on each relay.

 

[arivel]

[QUOTE = "canadaelk, post: 1384934, membro: 147525"]
Le schede tecniche dei relè avranno un grafico, simile all'allegato, che fornisce le informazioni necessarie. I contatti dei relè vibrano (si aprono e si chiudono più volte) fino a quando non si chiudono permanentemente dopo l'applicazione della tensione.
Il cablaggio dei relè in serie (utilizzando la tensione corretta) non cambierà questo dato che è una proprietà meccanica del relè. E
[/CITAZIONE]
si riflettendo devo essere d'accordo con te.

 

[picbits]

Also the common practice of placing BEMF diodes across DC coils causes a delayed drop out situation.
If you need high prescision synchronization, maybe look at a solid state solution.
Max.

I've used Zener diodes before as back EMF diodes for faster relay shut off.

 

[MaxHeadRoom78]

I've used Zener diodes before as back EMF diodes for faster relay shut off.

So there will be a degree of magnetic field left to collapse.
Max.

 

[canadaelk]

arivel: English please. As much as I would like to learn Italian....
The contact-bounce (chatter) can be reduced using a bifurcated relay. These type of relays are used in old telephone systems and any low-level circuit where relays (or switches) are employed.
When designing software a routine is called to wait for the end of the bounce before the next program is executed.
If timing is important a solid-state relay could be used. E

 

[Reloadron]

Simple description:

What is the Release Time of a Relay?

The Release Time of a relay is the transition time from the moment the voltage supply is stopped to the relay coil to the moment the normally open switch contact(s) open from its closed position.

When you supply a relay with its rated (or nominal) voltage, the normally open contacts up a relay close. However, when you remove the voltage from the relay coil, the normally open contacts that are closed snap back open (now that there is no power). The release time is the amount of time that it takes for the relay contact(s) to go from its closed position to its open position.

The Release Time of a relay includes the time for the magnetic field to weaken and cease (so the switch is no longer attracted, and, thus, closed), and the transfer time of the moveable contact (from its closed to its open position).

The Release Time for relays usually are in the milliseconds range; for example, a Panasonic JJM Series automotive relay has an release time of 10ms, when the voltage is cut off to the relay coil. The release time is usually comparable and, in fact, the same as the relay's operate time. This means that the time it takes for a relay's switch to close is usually the same as the time that it takes for a relay's switch to open.

When I was involved in some testing we measured what we called current decay time in the relay coil. Relays switching a few hundred volts and 70 amps we used a factor of about 15 mSec but the contact spacing was a pretty large gap.

Ron