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LED Charge Indicator

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find_beat

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Hey,

I'm starting on my summer project. I want to make a charging dock for my iPad with LED battery status indicator (Green - Charged, and Red - Charging).

I want to use a current comparator. So... iPad pulls high current when charging (red LED) and pulls low current when charged (green LED)

Can anyone recommend what should I use for the circuit? (cheap prices are always welcome).

Currently, I'm using the MCP6546 chip in multisim but I can't get the right current.
Source is 5V, 2 Amp... but so far my circuit can only provide uA and mV....
 
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hi,
The meter shows a current of ~17mA for the Green LED.?

The Red LED is off.
 
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Hey, Thanks for responding.

I just put meter everywhere to see how much Voltage and Amp is running around the circuit.

So the 1k ohms resistor is acting like an iPad (high R means low amp... so when iPad is fully charged, it pulls little to no current which is why Green LED is on)

I want to set the threshold current to be around .6 A.. but I'm not sure how to do it. Any advice?
 
The poor ipod simulation is the least of the problems with that circuit.

The fundamental poblem is that there does not appear to be any voltage dividers for the comparators, all the inputs are connected to +5v through an assortment of resistors with bizarre ohmic values.

JimB
 
Have a look at the attachment.

This is the bare bones of what your circuit should look like.

It is up to you to sort out the detail.

JimB
 
Thank you JimB,

I will do some digging and use ur circuit as foundation. Thank you so much. I'll get back to u guys with the result
 
Can you recommend any current comparator chip. Will the MCP6546-I/MS fit for this purpose?

ipad current can rang from ~0 to 1.6A
 
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I finished the simulation, but I'm not sure what symbol to use for the ipad... What symbol is for the "voltage source with internal resistance"?
 
I finished the simulation, but I'm not sure what symbol to use for the ipad... What symbol is for the "voltage source with internal resistance"?

You could use battery symbol with a resistor symbol in series with the battery

By alternately using Low and High charge batteries you could simulate charging/charged... use a series resistor that will allow the charge current to be typical.
 
I got the circuit to work. The problem is the chip (it operates in the mA range). Can anyone recommend another chip that would work for my purpose?

Thank You,
 
because I need AMPs going into the ipad but with the setup i have now... the current through ipad is in mA

hi.
I dont have an iPod, what is the battery type and voltage and the voltages you consider discharged and charged.??
 
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It is the iPad battery. Lithium. 42.5Whr battery. I used multimeter to measure the current draws while charging (0-99%) 1~1.5A.. and at full (100%) draws (~.5A). So I want to set the threshold around .6A?
 
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