- Sun Aug 20, 2017 6:18 pm
#69344
As I said in my last post. I would remove the existing shunt resistor. But it can be left in place and it's value would add to the external shunt. For example if the external shunt needed to pass 30 amps then the 3 amps that the existing shunt resistor passes could be compensated for by adjusting the the calibration register.
In my last product I needed to measure up to 120 Amps for overload current protection for a motor. (the second motor only required a 50 amps range for current limiting) I don't need 1% accuracy in that application 10% was more than sufficient.
50 Amp shunt resistors can be bought off Aliexpress for as little as $2 delivered. Are they a precision part? I doubt it, but for many applications the are good enough. Not everyone needs instrument quality devices for all their applications.
Yeah, that is the kind of thing I was saying 20 years ago when I could buy complete products for less than the cost of the parts. And I talking in about buying in manufacturing quantities. Yes it is hard to believe but they have been doing it for a couple of decades. If you think that low cost is automatically crap then why are you using the ESP8266? Or are you not buying the low cost modules. Instead you are purchasing components through traditional distribution and using locally manufactured boards. Because if you are then the modules will cost many time what the rest of us are paying.
As I have said, I have used those modules and they do work. And while the design is not exactly perfect they certainly are good enough for a lot of projects.
Edit
One more thing. Currently our company is buying all our PCBs fron China. North American manufactures just can't compete. And personally I have used the cheap prototyping pcb services, something like 10 pcs of 100mmx100mm boards for $10 usd. Quality was very good. Certainly as good as the prototype orders I had made that cost me $250 usd in country. (price converted from Canadian to USD)
In my last product I needed to measure up to 120 Amps for overload current protection for a motor. (the second motor only required a 50 amps range for current limiting) I don't need 1% accuracy in that application 10% was more than sufficient.
50 Amp shunt resistors can be bought off Aliexpress for as little as $2 delivered. Are they a precision part? I doubt it, but for many applications the are good enough. Not everyone needs instrument quality devices for all their applications.
Only with the Shenzen market "magic" you can have a brand new,genuine 1.5$ INA219 + a 5$ good quality shunt resistor and a well designed PCB for a complete device that will cost only 1.5$. yeah. magic. You know is no "magic" there. Just low quality, grey market or defective components.
Yeah, that is the kind of thing I was saying 20 years ago when I could buy complete products for less than the cost of the parts. And I talking in about buying in manufacturing quantities. Yes it is hard to believe but they have been doing it for a couple of decades. If you think that low cost is automatically crap then why are you using the ESP8266? Or are you not buying the low cost modules. Instead you are purchasing components through traditional distribution and using locally manufactured boards. Because if you are then the modules will cost many time what the rest of us are paying.
As I have said, I have used those modules and they do work. And while the design is not exactly perfect they certainly are good enough for a lot of projects.
Edit
One more thing. Currently our company is buying all our PCBs fron China. North American manufactures just can't compete. And personally I have used the cheap prototyping pcb services, something like 10 pcs of 100mmx100mm boards for $10 usd. Quality was very good. Certainly as good as the prototype orders I had made that cost me $250 usd in country. (price converted from Canadian to USD)
