AC/DC adapter voltage drops when 2 elements connected

Other Hardware General Electronics
1

Hi,

I made a circuit using a 9 volts AC-DC adapter to switch on 2 elements

In one hand, I have a voltage regulator with a LM317+ resistors and capacitors to give me at the end 3,7 volts to control a mini robot
In the other hand an Arduino board.
I know that my Arduino board needs 20 mA
My 3,7 volts robot needs 25 mA
My power supply has on INPUT : AC90/240V 50/60HZ and on OUTPUT : DC 9V 1A

Why when I plug the power supply and try to switch on both, it's not working ??
(I verified each element separately and they work perfectly )
So, what is wrong ? Is it a problem of current ? because I regulate the voltage ?
Sorry if this questions seem very simple, I'm still new in this area
Somebody can help me ?
Thanks :slight_smile:

2

How much current does each circuit take? Have you measure the current into each regulator under load?

Is the 9V power supply regulated or raw?

3

What about the ground ? I mean the negative of both supply goes together. Connected together.

4

All currents seem to be ok. the VIn is 9.11Volts, the Vout for arduino is 9.06Volts and for the voltage regulator 3.7Volts, which I need.
I tried different ways to connect all GND. It's working only when I have 2 separated power supplies. Seems to have a interference between GND and the sensor which command the mini robots (GND loop ?
An idea how to cut it ?

5

Post the Circuit please.

if you do not have a circuit making software ,get a light Newbie friendly FritZing.