Can the Songle srd-12vdc-sl-c relay be used with 12VDC on its output?
On top of the relay, it writes 10A 28VDC.
Can this 12VDC Relay be used for Switching 24VDC
relaysolid-state-relayvoltage
Related Solutions
I want to use relays for 5vdc control and 12vdc output with very low current. But I don't know if it is safe to use it or not.
If you are switching DC then you don't need an SSR - use a BJT or a MOSFET. Consider a MOSFET that is used in an off-line switching AC to DC converter - it might be switching 100,000 times per second and for 10+ years - is this enough?
Consider also that is it switching dc currents of a few amps at voltages up to maybe 400 V.
Also what about a class C RF amplifier operating at maybe 300 MHz - its output transistor is switching power at 300,000,000 times per second for possibly several years also.
If you do need galvanic isolation then a photo-voltaic optical coupler can be used to activate/deactivate the MOSFET exactly the same way SSRs use them. Same technology same long-life and gazillions of operations.
As @KevinWhite said, you can use a voltage controlled switch. Here is an example of a very rough model for a relay:
And this is the result of the simulation:
The model is very rough because:
- The excitation coil is modeled only by a resistor, neglecting the inductive component (this may be OK).
- The switch triggers when a voltage is applied to the terminals of the coil, whereas physically the relay triggers when the current in the coil is sufficiently high to move the contacts.
Both points above can be neglected unless you need to simulate the exact behavior of the relay under transient conditions (switching delays, oscillations, contact bounces, etc.).
An inductor in series with the coil resistance can be useful to simulate the inductive kick the relay produces when switched off.
Best Answer
Contact current has a direct affect on reliability, whereas voltage only affects open contact arc duration which is determined by load inductance. Since Relays are rated for typical usage, it would be impossible to define every application so they stick to standard automotive and truck voltage limits. Excess voltage and inductance such as from a motor could result in continuous contact arc and burnout quickly.
So in short any contact voltage less than rating is acceptable. However any current less than rating is not ok, but only specified by the few best manufacturers. It is a well known fact by thus author, that for low currents in the mA range, relay contacts rated >2A would be unreliable unless they have a capacitive load to arc through oxide which will quickly build up on any contacts rated >2A but used for extreme light current. Relays <2A often used in telecom often use gold plated to prevent oxidation. This may not apply to you, but is worth remembering to use 10% of rated current with capacitive surge current or resistive current MINIMUM. But the more current above this threshold will reduce contact switching life according to a log curve as shown in spec.
The other important fact on DC current ratings for relay contacts is that Inductive loads must be derated for current. For this part, I found the spec to be 50% or 5A instead of 10A DC.
The reason for MTBF vs contact current has to do with erosion of contact material in this case Silver- Cadmium-Oxide due to I^2*RtN for arc duration, t , contact resistance, R (which accelerates with age) and switch cycles, N.
So in short don't worry about less voltage, but be aware of the switched current relative to specs and added experience.