d123
Advanced Member level 5
Hi,
Suggested a circuit to a person on another forum, did it in a hurry and made an ass of myself as usual by making a silly mistake with the difference amplifier common-mode range when the OA is on a lower supply voltage to the PV panel voltage. I have tried to correct it myself by reasoning out that section, but I'm not certain if the solution is functionally correct by dividing down V2 and V1, then multiplying the V2 - V1 result by 50.
It's the voltage divider into Vin- feeding into the gain section of 500k/10k that I'm most unsure of.
1) Can someone say whether the difference amplifier section is correct for 5A across 10 mOhm resistor = 50mV across U1 Vin+ to Vin- = 2.5Vout. Not precise microvolt, just correct to a few mV or so. And that the common-mode range of U1 won't be violated?
As a 'rough sketch' circuit, can the whole thing work as desired, and at 5V op amp supply?:
1 Diff. amp: >5A across Rsense= >2.5V out
2 Current good: >5A = >2.5V ref = U2 high
3 Voltage good: >11.3V in = >2.5V ref = U3 high
4 AND op amp: U2 (= ~4.9V) + U3 (= ~4.9V) = U4 high (~4.9V out)
5 BMS enable pin
In other/less words:
1 > 50 mVin = 2 high
2 high + 3 high = 4 high
4 high = 5 high
Thanks.
Suggested a circuit to a person on another forum, did it in a hurry and made an ass of myself as usual by making a silly mistake with the difference amplifier common-mode range when the OA is on a lower supply voltage to the PV panel voltage. I have tried to correct it myself by reasoning out that section, but I'm not certain if the solution is functionally correct by dividing down V2 and V1, then multiplying the V2 - V1 result by 50.
It's the voltage divider into Vin- feeding into the gain section of 500k/10k that I'm most unsure of.
1) Can someone say whether the difference amplifier section is correct for 5A across 10 mOhm resistor = 50mV across U1 Vin+ to Vin- = 2.5Vout. Not precise microvolt, just correct to a few mV or so. And that the common-mode range of U1 won't be violated?
As a 'rough sketch' circuit, can the whole thing work as desired, and at 5V op amp supply?:
1 Diff. amp: >5A across Rsense= >2.5V out
2 Current good: >5A = >2.5V ref = U2 high
3 Voltage good: >11.3V in = >2.5V ref = U3 high
4 AND op amp: U2 (= ~4.9V) + U3 (= ~4.9V) = U4 high (~4.9V out)
5 BMS enable pin
In other/less words:
1 > 50 mVin = 2 high
2 high + 3 high = 4 high
4 high = 5 high
Thanks.