what can I use to replace a relay

Thread Starter


Joined Apr 5, 2024
Hi all
I'm extremely new to electronics and have a group college project I'm working on. My subsystem is a driver/dimmer unit for a set of 6 AC lamps. The circuit is responsible for receiving a digital signal and turning on an AC lamp, as well as dimming all 6 lamps by 60% their total brightness at night(low light). I've managed to find circuits and help to construct the attached circuit, note that some resistance values aren't fixed, as I was more concerned with getting a working circuit first and then work out the required values for dimming. my professor told me recently that a relay was not allowed to be used in this project, and as such I now am looking for ways that I can replace the relay with any other component and have it function the same. the only constraints of this project is that it must consist only of analog or digital components, and the exceptions are ICs. I used a clock pulse generator/steady edge to test the circuit when it is on, as there is another member's system responsible for turning certain lamps on/off. I started with one lamp to try to get the dimmer circuit working but need to expand to 6 more lamps(each with their own optoisolator/TRIAC-DIAC circuit), so I'd appreciate any advice on how to connect them as well. Screenshot 2024-04-08 221514.png


Joined Feb 20, 2016
You do not need a relay. The TRIAC and circuitry is all you need.
Have a read up on Zero Crossing Detector. Then, the brightness of the lamp can be controlled by generating the turn on pulse at a different time from the zero crossing. As you are running on AC mains, the control needs to be synced to the mains frequency, not just free running PWM.