In present day electronic we find many sensors or modules working in 3.3V logic levels.In other terms LVTTL devices (Low-voltage TTL). But even now we mostly use 5V TTL logic level uC or other devices with them. Hence, we need to change logic levels between 3.3V <---> 5V when interfacing both of them together. There are many dedicated chips for this and there was none available in the country. So I decided to build some simple circuits to do this conversion using transistors. Here,you can use any general purpose NPN transistors available in your country such as 2N39042SC828,BC547…etc. You need to supply 3.3V & 5V as shown in the schematics as Vcc. This won’t be a problem as you may already have these two power rails in your circuit as you use both for chips as Vcc. I have tested this on my 3.3V Bluetooth module interfaced with 5V PIC16F887.It worked well.