Showing posts with label relay. Show all posts
Showing posts with label relay. Show all posts
Thursday, October 20, 2016
Simple LED Relay Changeover Emergency Lamp Circuit
Simple LED Relay Changeover Emergency Lamp Circuit
The post shows how to configure a simple LED relay changeover emergency light circuit using a battery back up which gets charged during mains presence and changes over to LED/battery mode as soon as mains fails. The idea was requested by one of the members of this blog.
The following discussion explains the application details for the proposed LED relay changeover emergency lamp circuit
Hi,
I am trying to make very simple changeover circuit.. where I am using a 12-0-12 Transformer to charge a 12v Motorcycle battery via mains.. when the mains go off the battery will power a 10w LED. But, the problem is the relay is not switching off, when the mains goes down.. Any ideas. Want to keep it really simple..
12VDC Relay / 2200uf-50v cap on Transformer.
Hi, make sure that the relay coil is connected with the rectified DC from the 12-0-12 transformer. The relay contacts should be only wired with the battery and the LED
Hi Swagatam,
Firstly Thanks for the Reply.
1. Yes the Relay Coil is connected with the Rectified DC.
2. If I connect the relay contacts to Battery / LED only, then how will the Battery get charged when Mains is ON? If i am not missing anything..
The Design
The above circuit is self explanatory and shows the configuration for implementing a simple LED relay changeover emergency lamp circuit.
The following discussion explains the application details for the proposed LED relay changeover emergency lamp circuit
Hi,
I am trying to make very simple changeover circuit.. where I am using a 12-0-12 Transformer to charge a 12v Motorcycle battery via mains.. when the mains go off the battery will power a 10w LED. But, the problem is the relay is not switching off, when the mains goes down.. Any ideas. Want to keep it really simple..
12VDC Relay / 2200uf-50v cap on Transformer.
Hi, make sure that the relay coil is connected with the rectified DC from the 12-0-12 transformer. The relay contacts should be only wired with the battery and the LED
Hi Swagatam,
Firstly Thanks for the Reply.
1. Yes the Relay Coil is connected with the Rectified DC.
2. If I connect the relay contacts to Battery / LED only, then how will the Battery get charged when Mains is ON? If i am not missing anything..
The Design
The above circuit is self explanatory and shows the configuration for implementing a simple LED relay changeover emergency lamp circuit.
Available link for download
Tuesday, August 30, 2016
Triac SPDT Relay Circuit
Triac SPDT Relay Circuit
The post details a simple solid state triac SPDT relay circuit, using an optocoupler and a couple of triacs, which can be used as an effective replacement for mechanical relays. The idea was requested by "Cypherbuster".
In one of the other posts we learned how to make an DPDT SSR using mosfets, however this design could be used only for high current DC loads, and not with AC loads at the mains level.
In this article we will see how a simple mains operated solid-state relay can be made using triacs and an optocoupler.
The following figure show the details of the design:
The working of any relay is specifically intended to operate two different high power loads individually and alternately with the help of an external isolated low power trigger.
In a conventional mechanical type of rely this is done by toggling the loads across its N/O and N/C contacts in response to the activation applied across its coil.
However mechanical relays have their own drawbacks such as higher degree of wear and tear, lower life, generation of RF disturbance due to sparks across the contacts, and the most vital being the delayed switching response which could be crucial in systems like UPS.
In our triac SPDT relay circuit the same function is executed through the switching of two triacs via two BJT stages and an isolating optocoupler which ensures that the changeover operation for this relay has no drawbacks as mentioned above.
Referring to the diagram, the left side triac represents the N/O contact while the right side triac operates like the N/C contact.
While the optocoupler is in the non-triggered mode, the BC547 directly associated with the opto goes into the triggered mode, which keeps the second BC547 switched OFF. This situation enables the right side triac to remain switched ON, and the other triac is held switched OFF.
In this condition any load connected with the right triac becomes operational and stays switched ON.
Now as soon as a trigger is applied to the opto coupler, it switches ON, and in turn switches OFF the connected BC547.
This situation switches ON the second BC547 and consequently the right side triac is switched OFF, ensuring that the left side triac is now switched ON.
The above condition immediately toggles the second load ON and switches OFF the earlier load, effectively fulfilling the required alternate switching of the load with the help of an isolated external DC trigger.
The two LED connected with the bases of the two BJTs indicate which load is in the activated state at any moment while the triac SPDT relay circuit is being operated.
The above design could be further enhanced and made fully independent of an external DC power source by upgrading it with its own transformerless power supply, as shown below:
In one of the other posts we learned how to make an DPDT SSR using mosfets, however this design could be used only for high current DC loads, and not with AC loads at the mains level.
In this article we will see how a simple mains operated solid-state relay can be made using triacs and an optocoupler.
The following figure show the details of the design:
The working of any relay is specifically intended to operate two different high power loads individually and alternately with the help of an external isolated low power trigger.
In a conventional mechanical type of rely this is done by toggling the loads across its N/O and N/C contacts in response to the activation applied across its coil.
However mechanical relays have their own drawbacks such as higher degree of wear and tear, lower life, generation of RF disturbance due to sparks across the contacts, and the most vital being the delayed switching response which could be crucial in systems like UPS.
In our triac SPDT relay circuit the same function is executed through the switching of two triacs via two BJT stages and an isolating optocoupler which ensures that the changeover operation for this relay has no drawbacks as mentioned above.
Referring to the diagram, the left side triac represents the N/O contact while the right side triac operates like the N/C contact.
While the optocoupler is in the non-triggered mode, the BC547 directly associated with the opto goes into the triggered mode, which keeps the second BC547 switched OFF. This situation enables the right side triac to remain switched ON, and the other triac is held switched OFF.
In this condition any load connected with the right triac becomes operational and stays switched ON.
Now as soon as a trigger is applied to the opto coupler, it switches ON, and in turn switches OFF the connected BC547.
This situation switches ON the second BC547 and consequently the right side triac is switched OFF, ensuring that the left side triac is now switched ON.
The above condition immediately toggles the second load ON and switches OFF the earlier load, effectively fulfilling the required alternate switching of the load with the help of an isolated external DC trigger.
The two LED connected with the bases of the two BJTs indicate which load is in the activated state at any moment while the triac SPDT relay circuit is being operated.
The above design could be further enhanced and made fully independent of an external DC power source by upgrading it with its own transformerless power supply, as shown below:
Available link for download
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