IR leds drain battery too much??

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i have prepared a sensor circuit for my robot(pairs of IR led and photo-transistor).

i have used a series resistance of 100 ohms with led.
i have put 10k ohms as collector resistance.

the sensitivity of the circuit is excellent.

Now the problem is,the battery which i used for testing was getting drained too fast(i have attached the image of the battery that i used).when i checked the voltage across the output of the last transistor the voltage dropped to 3.7v ,where as i expected it to be well above 4.5v.(5v vcc for the sensor circuit)

for my robot i am using 2 bipolar steppers, i have planned to use 10 nimh batteries(2100mah)as battery source.will this combination be able to drive both my stepper and sensor circuit

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The 9V battery you show has VERY low energy storage. You waste almost 2/3 of that driving the LEDs. These batteries also have a rather high internal resistance; even alkaline ones SHOULD not be used with the heavy currents you seem to be using.

Why not use the NiMh batteries for the LEDs? It will be much more efficient AND they are designed for the high current.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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i have bought 10 ni-mh batteries for giving 12 v supply for my robot(2 steppers + sensor circuit).

since i hadn't charged them up, i tried using the above shown battery.

will these 10 nimh batteries(2100mah) be able to handle my 2 bipolar steppers(12v,8 ohms resistance per coil) and the sensor circuit for 20 min?

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vicky3413 wrote:
will these 10 nimh batteries(2100mah) be able to handle my 2 bipolar steppers(12v,8 ohms resistance per coil) and the sensor circuit for 20 min?

Well, take the 2100mAH and divide it by the sum of the stepper motor currents + the IRLED currents.

The result will be the length of time (in hours) the batteries will effectively power your system - minus any other current drains that you haven't told us about.

You can avoid reality, for a while.  But you can't avoid the consequences of reality! - C.W. Livingston

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You should also consider the pulse width you are using to drive the IR. You can use a very short 'on' part of the duty cycle, say 5%, instead of a 50% duty cycle for the carrier wave and it works as just as well and uses 1/10 the juice.

Smiley

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The OP did not say that the battery shown was LiMh. I thought it was 9V. That is why the voltages seemed very extreme.

The statements about mahr capacity and current drain given above are correct and need to be considered. Also, it is not trivial to charge these batteries and get full capacity stored IN them.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Hello!

I don't know if your interested in a project that appeared in EPE based on the TL499A designed to increase the efficiency of projects that use 9v batteries. This device can deliver 2000mah!!

http://www.epemag.com/0607p1.html

I don't know if this helps or not but, the output voltage is adjustable! When I read the original article I understood that this TI IC uses both "linear" and "switching" functions to maximize power efficiency...perhaps someone more schooled can explain the operation more fully??

John

Just some guy