Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

resistor or 7805

Status
Not open for further replies.

va_iv

New Member
Hi guys,

I am trying to convert 6V 300mA dc to
5V in order to give power to a pair of speakers
via USB

What is better to use? A 7805 regulator or some
kind of resistor (how Ω? )

thanks in advance for your help
 
A resistor is no good, the voltage will vary according to the current drawn through it - and a 7805 requires more than 6V input voltage to work. You can get LDO (Low Drop Out) regulators which would work with 6V input though.
 
usb is already at 5v ... do you mean you want to convert it to 6v?

with the voltages so close, it will probably work without any conversion, although you might want to use a self-resetting fuse or some other protection measure, to avoid burning out a usb port should something unexpected happen
 
Do you really need a fuse?

I thought usb ports have internal over current protection or am I wrong?
 
Speakers must be powered from a power amplifier, not from a power supply.
5V is a very low voltage for a power amplifier.

With a 5V supply, an LM386 power amplifier IC provides only 0.11W into an 8 ohm speaker at clipping. A little louder than headphones.
With a 6V supply, it provides 0.2W.
With a 9V supply, it provides 0.45W.
 
audioguru said:
Speakers must be powered from a power amplifier, not from a power supply.
5V is a very low voltage for a power amplifier.

With a 5V supply, an LM386 power amplifier IC provides only 0.11W into an 8 ohm speaker at clipping. A little louder than headphones.
With a 6V supply, it provides 0.2W.
With a 9V supply, it provides 0.45W.



thanks you all for your help.

actually I'm trying to connect HP speaker bar to another monitor. these HP speaker bar gets power from a usb cable. Unfortunatelly my monitor (eizo) gives 11.5V for speakers and i have some ac/dc power adapters that gives output 4.5, 6.0, .... 12V
 
justDIY said:
well if you have 11.5v available, just slap a 7806 (with heatsink) on it, and you're done (a 7805 could also be used, noting guru's caution of lower output)


thanks a lot .

I'll try both 7805 and 7806 (they are very cheap anyway).

be nice and healthy
 
va_iv said:
thanks a lot .

I'll try both 7805 and 7806 (they are very cheap anyway).

be nice and healthy

Hi,
if your aim to to power an external amplifier like lm386 using supply +5v from usb port,(provided the current is within limit), whay you want any conversion at all-- use 5V as vcc for the amplifier. as Audioguru indicated the output power will be less. No point in dc- dc conversion in my opinion.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top