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Sorry for the late reply. I was a little busy.
Yes the 1 ohm resistor is mostly redundant. In the actual circuit it will not be added.
I had used a balanced supply (+/- 19 volts) in the previous circuit. I have however revised it to a single supply basis, and attach it herewith.
You are right...
AlertLinks
Thanks for the circuit. However making a charge pump is out.
Anyway I seem to have made it work using a balanced power supply.
Schematic and PROTEUS files are attached.
Zeb
No luck. I downloaded and checked the datasheet. On page 15 there is an application circuit (Figure 25) for a Current Monitor. However there is a small note beside it which indicates the constraint that I have been talking about i.e. VL (in our case 24 VDC) should be 2 VDC less than or equal to...
I again need to emphasize. Please understand that there are UMPTEEN High side current sense ICs available int'ly. However these are not commonly available in Pakistan. I need to design with standard, easily available components - if possible discreet BJTs and FETs, so that once available in the...
Case Mod & AlertLinks.
By adding the voltage divider network the baby gets thrown out with the bathwater. Here the bath water is the 24 VDC and the baby is the mV drop across the shunt. I guess this is the reason they went ahead and invested in op-amps that can have input voltages equal to or...
AlertLinks and Casemod,
First let me thank you both profusely for taking the time out for your input. My very special thanks to AlertLinks for drawing up the circuits in PROTEUS. Most obliged.
Casemod,
I have described my my goals earlier which I reiterate below. I may repeat that the...
The advantages of high side over low side are many. You don't have to put a resistor (The Shunt- however small) between Ground and the Battery negative terminal. The most important - if a short to ground occurs the current would not pass through the shunt. So the problem remains undetected. You...
AlertLinks,
The method you are using is a cost effective replacement of a shunt. However it has the issue of variation with temp. etc, as described by Casemod. But I think for charging current measurement in the +/- 5-10% range it should be a good cost effective system. The only issue I have...
Brad,
We are now getting into the nitty-gritty of the design. I have thought through some but have to apply my mind to others.
Your observations about the use of car batteries are very pertinent. However what does one do when outside temp is 43 degC. In deep summer temp. goes upto 50degC. So...
Peter,
My purpose for this project is not specifically to design a charger but more generally a battery management system. Here in Pakistan we are in the midst of a serious energy crises with municipal power being available (worst case) for one hour in every two hours. So people use UPSs with...
Neddie,
As I submitted in my opening post all these ICs out there are not available in Pakistan. I am in fact trying to develop this charger for placement in the public domain (see below) so that somebody with a commercial intent can make and market. Access to sophisticated electronic...
Whilst all these approaches are possible, the main problem is the availability of various ICs and sensors. That is the reason I had to resort to the differential pair using discrete matched BJTs.
As per my original request please guide me about this approach.
Audioguru. Yes the CA3096 is...
Thanks guys for the responses.
Audioguru,
I looked at the TL081 datasheet. The absolute max rating for the op-amp input voltage is 15 volts. I am using 24 VDC battery. So the TL081 is out.
The BJTs used in the figure are out of necessity because PROTEUS does not have the data of CA3096 built...
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