Hello, this is my first post, so hopefully from all of the reading I have done so far, I can provide the necessary information for all you smart folks out there.
BACKGROUND: Recently purchased a new travel trailer that has a main switch control panel. This has a mixture of momentary and spst switches for various lights and equipment. The spst switches all illuminate and the momentary ones obviously do not. Interestingly all 4 of the momentary switches control lights outside of the unit that I cannot see and have to go out at night to tell if they are on or off. I tried replacing the momentary switches with the spst, but discovered that the trailer has something like a latching relay setup so you have the click the spst twice to get the lights to switch on, switch off (it is not an option to replace this latching setup as it is internal to the master control box of the unit)
I have been reading through a lot of posts here and I think I have found something that would work for me. The circuit utilizes a single XOR gate in the CD40470B which contains 4 in the standard IC, so to replace 4 switches so I could use one IC and the supporting discrete components, but I have a couple of questions based on this circuit. I have referenced the link here and the specific post is by Crutschow:
Pulse on closed circuit and on open again. (converting toggle switch to momentary) | All About Circuits
1. This circuit is based on 5v and my source would be 12v. The XOR IC looks to have an operating range that will work but I wanted to ask just in case there was any additional consideration there or with the discrete components.
2. It is my understanding that the duration of the pulse is controlled through the combination of R1 & C1. Is there a way to easily make this adjustable or is it a matter of determining what the optimum pulse duration is for the latching setup and calculate the R1 and C1 value to support that?
3. This circuit uses a 2N3904 transistor to control the relay. I'd like to replace this setup with a high power transistor such as the TIP120 so that I can control larger loads if needed (obviously with a heat sink). Are there considerations I should consider when using a transistor to switch the load rather than a relay?
I not an engineer but I have have a compute science background and I have experience creating simple circuit boards and projects etc.
Your help is greatly appreciated and please let me know if you have any questions.
Thanks.
BACKGROUND: Recently purchased a new travel trailer that has a main switch control panel. This has a mixture of momentary and spst switches for various lights and equipment. The spst switches all illuminate and the momentary ones obviously do not. Interestingly all 4 of the momentary switches control lights outside of the unit that I cannot see and have to go out at night to tell if they are on or off. I tried replacing the momentary switches with the spst, but discovered that the trailer has something like a latching relay setup so you have the click the spst twice to get the lights to switch on, switch off (it is not an option to replace this latching setup as it is internal to the master control box of the unit)
I have been reading through a lot of posts here and I think I have found something that would work for me. The circuit utilizes a single XOR gate in the CD40470B which contains 4 in the standard IC, so to replace 4 switches so I could use one IC and the supporting discrete components, but I have a couple of questions based on this circuit. I have referenced the link here and the specific post is by Crutschow:
Pulse on closed circuit and on open again. (converting toggle switch to momentary) | All About Circuits
Here's the LT spice simulation of the circuit I suggested.
The relay coil rating must be whatever the power supply voltage is. Its contacts are not shown.
Power and ground to U1 are not shown.
The six unused inputs in the U1 package must be grounded.
View attachment 138954
1. This circuit is based on 5v and my source would be 12v. The XOR IC looks to have an operating range that will work but I wanted to ask just in case there was any additional consideration there or with the discrete components.
2. It is my understanding that the duration of the pulse is controlled through the combination of R1 & C1. Is there a way to easily make this adjustable or is it a matter of determining what the optimum pulse duration is for the latching setup and calculate the R1 and C1 value to support that?
3. This circuit uses a 2N3904 transistor to control the relay. I'd like to replace this setup with a high power transistor such as the TIP120 so that I can control larger loads if needed (obviously with a heat sink). Are there considerations I should consider when using a transistor to switch the load rather than a relay?
I not an engineer but I have have a compute science background and I have experience creating simple circuit boards and projects etc.
Your help is greatly appreciated and please let me know if you have any questions.
Thanks.