4 tap questions again

[Nic]

So, I've built two of those.

One per BOM, works great
One, I've upped two dc-dc converter for higher current output.

I have problems, I was using my L4 to test bigger current draw, and maybe there is something wrong with the L4, BUT even with a simple fuz pedal that works on a 100mA output, I get noises from my 200 and 300 mA outputs.

I know I should really get more into understanding shcematics and basic circuitry... I'm wondering if I could need to upgrade the 100uf capacitors for the higher outputs (220 and 330) ?

On the 200mA, the L4 powers up but I think it barely makes it. On 300mA, it draint the power out of the 100mA outputs.

The voltage regulator has an output rated 1.5A, my wall wart puts 2A, so I don't think the problem comes from those.

 

[Nic]

Ok, so only some pedals seems to introduce noise. And on one of these I know there is a probles.... poorly grounded pedals maybe ?

 

[darwin999]

Yes, additional filtering may well be relevant. But your 'draining power' comment makes me nervous, so first let's check that out. Current isn't the only metric to consider, as we've got different voltages as we go through your circuit - e.g., for the wall wart, the 5V regulator, and the 9V outputs. E.g., 1A at 5V can at most convert to 5/9A at 9V. That L7805CV voltage regulator is 1.5A at 5V (so 7.5W), while you're drawing ~700mA at 9V (so 6.3W) - so those powers are almost comparable. And if we include the power efficiency of the DC-DC converters, which may be around ~80%, then that 7.5W at 5V may convert into just 6W at 9V. So you just might be asking to much from the L7805CV here... Just a thought.

 

[Nic]

Yes, additional filtering may well be relevant. But your 'draining power' comment makes me nervous, so first let's check that out. Current isn't the only metric to consider, as we've got different voltages as we go through your circuit - e.g., for the wall wart, the 5V regulator, and the 9V outputs. E.g., 1A at 5V can at most convert to 5/9A at 9V. That L7805CV voltage regulator is 1.5A at 5V (so 7.5W), while you're drawing ~700mA at 9V (so 6.3W) - so those powers are almost comparable. And if we include the power efficiency of the DC-DC converters, which may be around ~80%, then that 7.5W at 5V may convert into just 6W at 9V. So you just might be asking to much from the L7805CV here... Just a thought.

Thank you. I think I get what you are saying. I'll try to really understand it in the morning. But overall, bigger caps could help, but lets say a 2A regulator would be better.

Still, I think I need to check first how much current my L4 is drawing.

 

[darwin999]

Right, check the power at each point. Is that an Aion L4? The Aion L4 power was discussed in another thread recently, I think it was around 200mA - i.e., a lot. Enjoy your weekend.

 

[darwin999]

USB Power

Not sure where I messed up... I did not take the exact parts from the BOM for the DC-DC and the voltage regulator, maybe I missed something because they look like equivalent parts. Yesterday, I had problems with my L4 running on battery, so I thought that it was a good time to test the USB...

forum.pedalpcb.com

I'm measuring the current draw at 190mA.

 

[Nic]

Right, check the power at each point. Is that an Aion L4? The Aion L4 power was discussed in another thread recently, I think it was around 200mA - i.e., a lot. Enjoy your weekend.

Yes, that was my post. The answer I got was from Kevin at aion. I will measure mine, I have a feeling it's higher and will need to figure why if it is. Thanks again.

 

[Nic]

I guess my little dmm has it's limits. I know for sure it goes up to aroung 150mA, but them it beeps and retries... at this point, I might try a reflow and maybe bigger caps.