just got the TI "sample" boards

[codfish124]

i have built this mod im not reducing the volts the resistor is added to the booster board to change the out put voltage. through the booster board you can go all the way up to 15 volts from 3.7 volts using diferant resistors.

but you bring up a good option. if i wanted to use a 9v battery would the Silicon rectifiers consume energy so i would be going through batteries faster or do they just drop the volts. how is the current affected.

 

[Nuck]

the site says "minimum out" of 5v..you're runnin *that* through a resistor to drop it further then? I still don't know why no one is using silicon rectifier diodes to drop voltages in predictable approximately 1v incriments lol, that was the golden standard back in the day for high amperage small voltage drops. Silicon rectifiers basically reduce *through* voltage by their switch-on value... if it requires 1.2v to switch on, then voltage passing through it will be reduced by that amount, and radio shack used to sell them in bulk for cheap...and everyone else would be cheaper. Only issue is that you cant reverse the battery..you gotta pick a direction and stick with it as voltage only goes one way through a diode

With just 1 extra resistor you can "fool" the boost converter into outputting lower voltages which is a much better solution than wasting bat life with in-line resistors/diodes.

As long as you are careful to ensure the output is above input voltage it works very well and saves a lot of energy. After testing with quite a few mods and 401/510/801 and 901 attys the values I use are 4.4, 4.6, 4.8 and 5.0 on my mods. The voltage under load tends to climb about 0.1v with this board.

 

[Nuck]

Folks have done plenty of builds using the 1n4001 rectifier diodes to pull 6v down to 5v.

Pulling 8v down to 5v, the LDO regulators seem to be more popular.

Now, the trend is going toward using boost converters to push 3.7v up to 5v, which has the advantage of letting you use batteries in parallel for longer duration.

In both cases (the LDO regulators and the boost converters), you have stable voltage all the way to cutoff - not the case with the 1n4001 diodes.

Another benefit to the one cell boost method is that you can then add a USB charge port to the mod quite cheaply. Not possible with a 2 bat series solutions.

 

[Marctwo]

With just 1 extra resistor you can "fool" the boost converter into outputting lower voltages which is a much better solution than wasting bat life with in-line resistors/diodes.

As long as you are careful to ensure the output is above input voltage it works very well and saves a lot of energy. After testing with quite a few mods and 401/510/801 and 901 attys the values I use are 4.4, 4.6, 4.8 and 5.0 on my mods. The voltage under load tends to climb about 0.1v with this board.

How? Is this mentioned in the datasheet?

 

[Marctwo]

Can anyone expand on this - Vo < 5V?

The formula in the datasheet would have me using -53K for 4.4V... but I don't have any of those.

Is it actually an extra resistor that's needed or just a larger one for the adjust?

I'll be able to mess about with this as soon as my board arrives but it would be nice to have the benefit of tried & tested values/formulae.

 

[Marctwo]

Maybe I need the secret handshake.

Anyway, if anyone's interested, my board arrived and I managed to find a -36K resistor that gave me 4.35Vo and a -4K7 that gave me 3.64Vo.

I just need to test under load and see what Vi > Vo is like.