Getting 5V from 6V source

[reuben90]

Hi,

I need 5V to power up a receiver whose ratings are marked 5V, 5.5mA max. My idea of obtaining this voltage is to stack up 2 button cells of 3V each, since space is of concern. However, this will give me 6V and I thought of this to bring it to 5V:

Requirements of Receiver
V = 5V
I = 5mA
so R = 1kohm (resistance of receiver)

Plan: Add resistor R1 to bring down voltage supplied to receiver (R).

V = I (R + R1)
I = 5mA
R = 1kohm
V = 6V
Therefore, R1 = 200ohms. So, if I add this resistor, I should get 5V in my receiver and maintain 5mA current. I was hoping if someone can confirm this or am I missing something.

 

[Gryd3]

Hi,

I need 5V to power up a receiver whose ratings are marked 5V, 5.5mA max.
....
Therefore, R1 = 200ohms. So, if I add this resistor, I should get 5V in my receiver and maintain 5mA current. I was hoping if someone can confirm this or am I missing something.

Your resistor will only drop the supply down to 5V when it is under a 5mA load.
The supply voltage would be 5.2V at 4mA load.
I do not know what components your device is using, but they typically have a min/max rating that you can supply. If you can, pop it apart and look at a data sheet.

Myself... I would probably just use a diode with a 0.6 - 0.7V voltage drop and call it a day. But that depends on what the part is that I'm trying to power and if someone else jumps in here, verbally smacks me, and tells me why I should not do it XD

Edit: The community here is great, I won't get smacked very hard unless I am forgetting something that would cause my diode solution to self-destruct.

 

[BobK]

At 5mA, probably 2 diodes.

Bob

 

[(*steve*)]

Given the low current, I'd use a 5.1V zener diode and a 100 ohm resistor, taking the approximately 5V from across the zener.

The voltage may be a little low due to the lowish zener current. Dropping the resistor to 47 ohms should rectify that.

 

[reuben90]

Thanks Gryd3, Bob, steve, I am going to give diodes a try.