Al,
I've got a LM7805 that I'll splice in to get the 5v I need.
I don't think the drop in output will be a big deal. We'll see, but I'm guessing the field coil won't need 12v for the stator to output in excess of 12v.
Thanks again for the help.
--Kurt
manage load with digital pot
Two AD5220s quit on me during testing this weekend when the voltage got too low.
When I run my well pump off of the inverter, the surge to start it drops the voltage way down (not sure how far, but it's below 10.5v because the inverter alarm sounds).
More testing required. Otherwise, things are working REALLY well.
When I run my well pump off of the inverter, the surge to start it drops the voltage way down (not sure how far, but it's below 10.5v because the inverter alarm sounds).
More testing required. Otherwise, things are working REALLY well.
Kurt - SF Bay
Hi again Kurt,
Have any idea why the AD's are blowing out?
I think using the 5 volt regulator chip to power them is a good
idea really.
The only idea i have for the blow outs is that maybe you can not
apply input signals to that 'pot' unless it has it 5 volt supply line
active. Without the 5 volt supply the signal lines might be trying
to drive the power of the chip through input protection diodes.
This is a problem i had with my AD converter too. I had to add
resistors in series with the input signals to limit the current into
the input pins when the power supply for the chip went down.
Have any idea why the AD's are blowing out?
I think using the 5 volt regulator chip to power them is a good
idea really.
The only idea i have for the blow outs is that maybe you can not
apply input signals to that 'pot' unless it has it 5 volt supply line
active. Without the 5 volt supply the signal lines might be trying
to drive the power of the chip through input protection diodes.
This is a problem i had with my AD converter too. I had to add
resistors in series with the input signals to limit the current into
the input pins when the power supply for the chip went down.
LEDs vs Bulbs, LEDs are winning.
That's gotta be it! I've got one supply for the stamp and one for the AD5220(s). Here's why:
Any time the ratiometric VC has power applied, the alternators get a field current and start charging with a few amps. To prevent this during motor start and other conditions, I put a relay in line with the power feed to that part of the breadboard.
The AD5220 failure is characterized by a "stuck" value. That is, they still pass signal, but they don't respond to up/down ticks anymore. It makes sense that the control side is what's getting zapped and not the wiper.
Thanks Al.
--K
Any time the ratiometric VC has power applied, the alternators get a field current and start charging with a few amps. To prevent this during motor start and other conditions, I put a relay in line with the power feed to that part of the breadboard.
The AD5220 failure is characterized by a "stuck" value. That is, they still pass signal, but they don't respond to up/down ticks anymore. It makes sense that the control side is what's getting zapped and not the wiper.
Thanks Al.
--K
Kurt - SF Bay
Al,
I used the circuit you designed for last weekend to keep my battery bank charged. Worked great! Thanks again.
I've got some tweaking to do...still blowing AD5220s. This is probably because I haven't place the resistor in-line to protect it when there no power to the chip as you suggested. It think the problem is being exacerbated by my cutting power to each of the four voltage controller circuits as power from their connected alternators isn't needed when the batteries get close to peak charge.
This brings up another point: the minimum charge I can set the alternators to is ~10A. With all of their field coils connected, I get ~40A. My current remedy is to cut power to each of the four circuits I copied from your design in succession until the last one pushes my battery voltage too high at which point I kill the gas engine. Is there a change I can make to your circuit that will drop the field current to a point where my lowest setting results in zero output from the alternator?
I had another thought about gain, too. It would be great to feed the 13+ volts from the battery bank while charging into the LM358 instead of just the ~5v from the AD5220 and get more gain (I'm presently getting only 40A max each from my alternators). Referring to your schematic, could I do this with a transistor (3904 perhaps) between the AD5220 (pin 5) and the LM358 non-inverting side with the collector connected to BAT+? This way, I'd be powering the AD5220 with my LM7805 and the ratiometric voltage controller with all the voltage the battery bank/alternators had to offer. Lost cause? Let me know and I'll try doing the required math.
Thanks again,
Kurt
I used the circuit you designed for last weekend to keep my battery bank charged. Worked great! Thanks again.
I've got some tweaking to do...still blowing AD5220s. This is probably because I haven't place the resistor in-line to protect it when there no power to the chip as you suggested. It think the problem is being exacerbated by my cutting power to each of the four voltage controller circuits as power from their connected alternators isn't needed when the batteries get close to peak charge.
This brings up another point: the minimum charge I can set the alternators to is ~10A. With all of their field coils connected, I get ~40A. My current remedy is to cut power to each of the four circuits I copied from your design in succession until the last one pushes my battery voltage too high at which point I kill the gas engine. Is there a change I can make to your circuit that will drop the field current to a point where my lowest setting results in zero output from the alternator?
I had another thought about gain, too. It would be great to feed the 13+ volts from the battery bank while charging into the LM358 instead of just the ~5v from the AD5220 and get more gain (I'm presently getting only 40A max each from my alternators). Referring to your schematic, could I do this with a transistor (3904 perhaps) between the AD5220 (pin 5) and the LM358 non-inverting side with the collector connected to BAT+? This way, I'd be powering the AD5220 with my LM7805 and the ratiometric voltage controller with all the voltage the battery bank/alternators had to offer. Lost cause? Let me know and I'll try doing the required math.
Thanks again,
Kurt
Kurt - SF Bay
Hi again Kurt,
From what you are saying it could be that something isnt working
right yet. Perhaps we should preform a few tests to find out
if everything is working as it should be.
For example, the circuit is set up to put out a max of about
2v at low setting. I would think this would be low enough,
but if the circuit isnt working right we might be getting
a higher output like maybe 4v. Also, there may still be
issues with the digital pot and i think that before we do
anything else we should replace one channel with a 'real'
pot of the same value and do the tests like that.
Test1:
When the real pot is set lowest measure the output voltage.
Test2:
When the real pot is set highest measure the output voltage.
These two simple tests will tell us a lot more and allow us
to determine what has to be done to get your required operation.
As far as your gain concern goes, we dont have to feed any more
than +5v into the op amp because the gain of the op amp is
made to increase that value so it makes it look like the pot
goes from 0 to 10v instead of 0 to 5v. No problem there.
If you do think you need more gain, we can verify that more
gain will help once we get the measurements above.
You can also do another test:
Test3:
Change the 10k resistor that connects to the output of the
op amp to 12k. Set the pot to maximum again and again measure
the output voltage (with load BTW).
Ok, so we have three tests in all and they should all be done
with load of course. Remember you only have to modify one
single channel for these tests so you only need one real
pot and one 12k resistor.
Let me know what results you get and we can go from there.
BTW, do you know what the min and max capability of your
alternators is, as to what they can do if driven properly?
PS.
I also re-read the data sheet and it looks like we should not really
be putting 6.2v on the digital pot resistor terminals. The max we
should be putting there is 5v, so that means a 4.7v zener would be
a better choice for the zener diode (rather than 6.2v). This would
keep the pot voltages under 5v which is better for the ic chip being
used. Note that proper operation will not be obtained without doing
this kind of fix (resistor and zener as per schematic) because the
chip will be overdriven on at least one usually important spec.
Of course this means the first thing to do to at least one channel
for testing is to add that 10k resistor and 4.7v zener. If you want
to stay ratiometric you can calculate the resistor value required to
assure 5v at the top of the digital resistor (top terminal of ic) with
your highest measured input voltage (might be +12 to +14 volts
or maybe even a little higher), and you can then make the zener
voltage a little higher, like 5.2v or something like that.
For example, with a 14v max an 18k resistor would be required,
with a 5.2v zener.
From what you are saying it could be that something isnt working
right yet. Perhaps we should preform a few tests to find out
if everything is working as it should be.
For example, the circuit is set up to put out a max of about
2v at low setting. I would think this would be low enough,
but if the circuit isnt working right we might be getting
a higher output like maybe 4v. Also, there may still be
issues with the digital pot and i think that before we do
anything else we should replace one channel with a 'real'
pot of the same value and do the tests like that.
Test1:
When the real pot is set lowest measure the output voltage.
Test2:
When the real pot is set highest measure the output voltage.
These two simple tests will tell us a lot more and allow us
to determine what has to be done to get your required operation.
As far as your gain concern goes, we dont have to feed any more
than +5v into the op amp because the gain of the op amp is
made to increase that value so it makes it look like the pot
goes from 0 to 10v instead of 0 to 5v. No problem there.
If you do think you need more gain, we can verify that more
gain will help once we get the measurements above.
You can also do another test:
Test3:
Change the 10k resistor that connects to the output of the
op amp to 12k. Set the pot to maximum again and again measure
the output voltage (with load BTW).
Ok, so we have three tests in all and they should all be done
with load of course. Remember you only have to modify one
single channel for these tests so you only need one real
pot and one 12k resistor.
Let me know what results you get and we can go from there.
BTW, do you know what the min and max capability of your
alternators is, as to what they can do if driven properly?
PS.
I also re-read the data sheet and it looks like we should not really
be putting 6.2v on the digital pot resistor terminals. The max we
should be putting there is 5v, so that means a 4.7v zener would be
a better choice for the zener diode (rather than 6.2v). This would
keep the pot voltages under 5v which is better for the ic chip being
used. Note that proper operation will not be obtained without doing
this kind of fix (resistor and zener as per schematic) because the
chip will be overdriven on at least one usually important spec.
Of course this means the first thing to do to at least one channel
for testing is to add that 10k resistor and 4.7v zener. If you want
to stay ratiometric you can calculate the resistor value required to
assure 5v at the top of the digital resistor (top terminal of ic) with
your highest measured input voltage (might be +12 to +14 volts
or maybe even a little higher), and you can then make the zener
voltage a little higher, like 5.2v or something like that.
For example, with a 14v max an 18k resistor would be required,
with a 5.2v zener.
LEDs vs Bulbs, LEDs are winning.
Al,
I think I'll be able to run some tests over the weekend.
Here's some more pics of the prototype and battery bank:
I'll take some pics of the wiring next time.
Though slightly off-topic, here are some pics of the peace and quiet we get to enjoy in the silence of a fully-charged battery bank:
Enjoy!
I think I'll be able to run some tests over the weekend.
Here's some more pics of the prototype and battery bank:
I'll take some pics of the wiring next time.
Though slightly off-topic, here are some pics of the peace and quiet we get to enjoy in the silence of a fully-charged battery bank:
Enjoy!
Kurt - SF Bay
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