hungmao

Hi, I'm a newbie here. I just want to share some experience in doing this project since many problems encountered are very similar to other big brothers. I have done this project with Smart Kit version and created the PCB with information in this webpage. Mine is configured in 20v DC range. In the very beginning, after I have finished, I found that the measured voltage cannot be locked with fluctuation of about 0.6v (my measured voltage should be regulated 4.5v, fluctuation range = 4.2v to 4.8v). I have measured the target voltage with another multimeter and confirmed that this voltage is stable. After the troubleshooting, I found that the following steps can help to mitigate the problems: (1) flux residues must be clear after soldering. (2) my voltmeter sourced by LT1085 regulated in +5v and attain -5v from ICL7660. But, my transformer's secondary output shared command ground with another power supply(9v-0-9v). The fluctation problem is mainly come from here. After separated the transformer, the fluctation solved in a great extent with only 0.05v (acceptable range for me). (3) proper grounding and shielding for the voltmeter circuit. Just my two cents. Hopefully these can help.