I am new to this forum. I am a Diploma in Electronics from India and a passionate DIY hobbyist too.
I have a question regarding cheap 10 amp ammeter and a voltmeter module I bought off aliexpress.
I am building a variable DC PSU using a 24 volt 10 ampere SMPS as the main power source and feeding its output to a cheap XL4016E1 based buck converter which has CC CV Control. I have done all connections right and the PSU works fine on 230 V AC. Now I want to run the buck converter on external DC input (I have installed protection diodes to prevent clashing of the SMPS output with the external DC input) and was wondering whether the voltmeter ammeter module will need an isolated DC DC converter module to power it up to prevent damage to it while I run the entire PSU on external DC input, or should I simply think of installing a 9 volt battery to power the voltmeter ammeter separately and activate battery power only when external DC supply is detected at the DC jack by using a relay.