I got 2 lm317 circuits both adjusted to output 2.78 volts they're powered from a single 5v usb adapter my goal is to power two wiimotes simultaneously from the same power source. when i check the circuits with a multimeter i get 5.2v input and 2.78 output on both circuits but when i plug both wiimotes in and turn them on they only power on for a few seconds then the led indicator light on the circuit goes dim and both wiimotes turn off. i wait a few seconds and the ligt gets bright again. i'm guessing i need to install an amp some where on the circuit but i dont know how to go about doing this and i have limited space on my perfboard.

 

How much current do the WIImotes take? Do the regulators get hot?

 

2.5 - 3v and 15-35Ma and the regulators stay cool

 

Could you post a schematic of the regulator circuits?

 

hope its legible lol

https://scontent-b-iad.xx.fbcdn.net/hphotos-ash3/t1/1897948_1426642854240659_1831127575_n.jpg

 

Have you tried monitoring the input and output voltages during the startup/shutdown or just made static readings?

 

My guess would to much current draw ...
Why don't you use a different voltage regulator and instead of running a dual voltage regs ,only use one and tap off the output ??
Also the lm317 need atleast 10ma each..

 

If your currents are accurate then they are not the problem and I think you easily meet the regulators' minimum current.

How about the quality of your solder joints?

 

Your schematic looks pretty bone standard imo, so barring a bad regulator i wouldn't personally expect there to be any problems at all with the design. Based on what you describe, and more importantly that fact that your indicator led is before the lm317's, i would guess that the problem is actually in whatever supply you are using to power it with.

You say you are drawing 35 mA per regulator output, your also going to have 5 or 6 mA being pulled down by the sense resistors on each regulator, then some exess power dissipating by voltage drop across the regulators, and another 15 mA or so burned off by the LED, so your probably drawing overall around [speculation] 110 or so mA overall. If this circuit is being power by a standard computer USB port, from what i've read, its not uncommon for certain ports to be limited to 150mA or so MAX, so you may just be close to the limit of current draw from your power source. Either that or the transient response of your power source is too slow, the current spike when you turn stuff on and it takes a second for the source's regulator to catch up. Try using a different port (i think current limit depends on port? someone correct me if im wrong) as some ports on a motherboard will have a cap of 500mA. Or maybe try a USB phone charger?

Best bet would be to put a meter on the input lines (better still a scope if you have one) and see if theres a voltage drop when you make your connections. Should at least narrow it down.

BTW: awesome choice for a project enclosure

 

Your schematic looks pretty bone standard imo, so barring a bad regulator i wouldn't personally expect there to be any problems at all with the design. Based on what you describe, and more importantly that fact that your indicator led is before the lm317's, i would guess that the problem is actually in whatever supply you are using to power it with.

You say you are drawing 35 mA per regulator output, your also going to have 5 or 6 mA being pulled down by the sense resistors on each regulator, then some exess power dissipating by voltage drop across the regulators, and another 15 mA or so burned off by the LED, so your probably drawing overall around [speculation] 110 or so mA overall. If this circuit is being power by a standard computer USB port, from what i've read, its not uncommon for certain ports to be limited to 150mA or so MAX, so you may just be close to the limit of current draw from your power source. Either that or the transient response of your power source is too slow, the current spike when you turn stuff on and it takes a second for the source's regulator to catch up. Try using a different port (i think current limit depends on port? someone correct me if im wrong) as some ports on a motherboard will have a cap of 500mA. Or maybe try a USB phone charger?

Best bet would be to put a meter on the input lines (better still a scope if you have one) and see if theres a voltage drop when you make your connections. Should at least narrow it down.

BTW: awesome choice for a project enclosure

I was actually running it from a 5v Lg cellphone usb charger that was plugged into a 120 house line. but now instead of splitting the line i ran both circuits to there own 5v chargers boxes. I got 2 usb male plugs hanging out the nes controller now kind of a sausage fest but i needed to get a working model. it works fine no problems so far but I definitely still wanna get it working of one power source. I got like 50 different voltage regulators in my inventory I can try but I haven't researched them yet I not hip to their specs

 

My guess would to much current draw ...
Why don't you use a different voltage regulator and instead of running a dual voltage regs ,only use one and tap off the output ??
Also the lm317 need atleast 10ma each..

What would you recommend I have a ton of different regulators i've pulled off boards im not hip to their specs though. I probably got at least 50 different types

 

There are hundreds upon thousands of regulator IC's out there. It would be much easier if you simply created a list of what you have available, and post it.

However, I suggest that you try using a 100uF to a 10,000uF cap on the input side, and a 10uF on each regulator output, and see if this affects a change.

 

get 5.2v input and 2.78 output

That leaves only 2.42V across the regulator, which is close to the drop-out voltage of an LM317, especially if the input voltage sags under load. Perhaps you need a low drop out regulator instead?

 

There are hundreds upon thousands of regulator IC's out there. It would be much easier if you simply created a list of what you have available, and post it.

However, I suggest that you try using a 100uF to a 10,000uF cap on the input side, and a 10uF on each regulator output, and see if this affects a change.

here's a list of regulators it's not the complete list of what I have but if none of these will work ill go de-solder some more

LA6500 3v6
4236 d5lc20u
KIA 7805A
D882
KIA 7808A
STV9375 842334Z
A2005
3601 K2251
C5511
02688
0138 D1c504M
2636 D5LC20U
C5682 3f4
SE140 3611N
KIA 7812A
LA6500 3v0
K2876
C4632
79M12A JRC M303fG
LA6500 3v7


I haven't tried your suggestion with the capacitors yet because I dont have any available but if i cant get any regulators to work im make a run to radioshack

 

I tweaked my design a tad I'm know trying to power 4 wiimotes. I'm getting a 2.78v reading on all four outputs but I can still only power one wiimote at a time and the regulator get ver hot if i plug in more then one remote hmmmmm....

 

here's the schematic of the new circuit. https://scontent-b-ord.xx.fbcdn.net/hphotos-ash3/t1.0-9/1010112_1431088443796100_1129035960_n.jpg

when I have two wiimotes connected i'm getting a steady 3.08v on all four outputs but randomly when I'm turning them on and off or plugging and unpluging/ switching ports I'll hear this sound like a dog whistle and my voltage drops below 0.5v and the regulator gets super hot.

i was thinking there might be short somewhere but everything looks good on that end. any thoughts?

 

You may have a bad capacitor or one connected backwards.

 

Well I got the circuit working working 100% it's been in operation for 3 days with no problems I made some changes though I have 5v going to two usb outputs and to lm317 adjusted to 3.13v going to two usb outputs. the 3v powers two wiimotes and 5v powers sensor bar and 3 leds in my arcade buttons which are wired to a keyboard pcb