Well some weird things are going on here. I found that using
1: 100k single gang pot OR 500k single gang pot
2: 1k resistor in series with 5VDC and the wiper of the pot
3: A single 681R resistor from pot to each series resistors and another 681R in series to each shunt for a total of 4 681R resistors.
Produces some weird readings when turned all the way up or down. For instance when I turn it all the way up, in the last 1/4 or so of the pot, the shunt LDRs increase, decrease, increase, and finally decrease in resistance.
This particular set of LDRs gives me 48.2k at full turn with a 100k pot. WEIRD.
With the 500k pot I get the same weird rise and fall of resistance in the last 1/4 turn. Resistance of same LDR in shunt position gives me rise and fall that centers around 140-170k until it skyrockets to 1.4MOhm.
Change the setup now
1. Same two pots
2. Same 1k resistor
3. A total of 2 681R resistors after the pot. One feeding both series and one feeding both shunt LDRs.
Same thing happens with 500k pot except that it wobbles around 130k and then skyrockets to only 400k.
100k pot produces slight wobble from 10-12k and wobble from 20-23k where it ends. Max resistance was 23k.
Change setup again
1. Same two pots
2. Same 1k resistor
3. Thats it. No resistors after the pot
100k pot produces wobbles at 10-12k and 15-19k then ascends rapidly to over 100k and then skyrockets to 790k.
500k pot produces wobbles from 250k to 300k then skyrockets into the 10MOhm and higher range. It basically turns off.
Change setup again
1. Same two pots
2. No 1k resistor
3. 1 681R resistor for each LDR
500k I get wobble from 100-230k then when I hit 400k it dives back down to values near 100k. There is a max value in there of around 600k but its not at full turn and its right near 400k. Very odd.
100k I get I get a good rise til 6k and it wobbles til 9k and then dives to 6k and stays there for maybe 1/5th of a turn, the last 1/5th of the pot.
Change setup again
1. Same two pots
2. No 1k resistor
3. 2 681R resistors - 1 for shunt and 1 for series
100k pot I get wobble from 6-8k then slow dive to 5.9k for last bit of the pot.
Next I will try the same experiments with a dual gang 100k pot. Unfortunately I dont have a 500k dual gang to try.
Okay 100k dual gang pot-------------------------
1: 100k dual gang pot wired as George shows
2. No 1k reistor
3. 4 681R resistors. One for each LDR
Perfect rise to 2.5k
1. Same 100k dual gang pot
2. No 1k resistor
3. 2 681R resistors, 1 for series and one for shunt
Perfect rise to 7k
1. Same 100k dual gang pot
2. 1k resistor in series with 5VDC to pot as instructed by George
3. No 681R resistors
NO WOBBLE Perfect control to 1MOhm
1. Same 100k dual gang pot
2. 1k resistor as last experiement
3. 2 681R resistors, 1 for series and one for shunt
NO WOBBLE Perfect control to 28.4k
1. Same 100k dual gang pot
2. 1k resistor as in last experiment
3. 4 681R resistors, 1 for each LDR
NO WOBBLE Perfect control to 59k
SOOOOooooOOO
In this experiment I used 20VDC going to a LM7805 with .33uf and .1uf ceramic caps on the regulator. I used no parallel resistor as I have suggested in the past and I dont know what the effect would have been.
There is my data. Take it for what its worth but my recommendation today is to use dual gang pots for stability and to get the best use out of the LDRs.
Next I will do the same experiments with the original Lightspeed circuit and the same 4 LDRs I just tested. I have 100R resistors in place to test but its time to make dinner and this sometimes takes up to much time.
Interesting stuff.
Uriah
1: 100k single gang pot OR 500k single gang pot
2: 1k resistor in series with 5VDC and the wiper of the pot
3: A single 681R resistor from pot to each series resistors and another 681R in series to each shunt for a total of 4 681R resistors.
Produces some weird readings when turned all the way up or down. For instance when I turn it all the way up, in the last 1/4 or so of the pot, the shunt LDRs increase, decrease, increase, and finally decrease in resistance.
This particular set of LDRs gives me 48.2k at full turn with a 100k pot. WEIRD.
With the 500k pot I get the same weird rise and fall of resistance in the last 1/4 turn. Resistance of same LDR in shunt position gives me rise and fall that centers around 140-170k until it skyrockets to 1.4MOhm.
Change the setup now
1. Same two pots
2. Same 1k resistor
3. A total of 2 681R resistors after the pot. One feeding both series and one feeding both shunt LDRs.
Same thing happens with 500k pot except that it wobbles around 130k and then skyrockets to only 400k.
100k pot produces slight wobble from 10-12k and wobble from 20-23k where it ends. Max resistance was 23k.
Change setup again
1. Same two pots
2. Same 1k resistor
3. Thats it. No resistors after the pot
100k pot produces wobbles at 10-12k and 15-19k then ascends rapidly to over 100k and then skyrockets to 790k.
500k pot produces wobbles from 250k to 300k then skyrockets into the 10MOhm and higher range. It basically turns off.
Change setup again
1. Same two pots
2. No 1k resistor
3. 1 681R resistor for each LDR
500k I get wobble from 100-230k then when I hit 400k it dives back down to values near 100k. There is a max value in there of around 600k but its not at full turn and its right near 400k. Very odd.
100k I get I get a good rise til 6k and it wobbles til 9k and then dives to 6k and stays there for maybe 1/5th of a turn, the last 1/5th of the pot.
Change setup again
1. Same two pots
2. No 1k resistor
3. 2 681R resistors - 1 for shunt and 1 for series
100k pot I get wobble from 6-8k then slow dive to 5.9k for last bit of the pot.
Next I will try the same experiments with a dual gang 100k pot. Unfortunately I dont have a 500k dual gang to try.
Okay 100k dual gang pot-------------------------
1: 100k dual gang pot wired as George shows
2. No 1k reistor
3. 4 681R resistors. One for each LDR
Perfect rise to 2.5k
1. Same 100k dual gang pot
2. No 1k resistor
3. 2 681R resistors, 1 for series and one for shunt
Perfect rise to 7k
1. Same 100k dual gang pot
2. 1k resistor in series with 5VDC to pot as instructed by George
3. No 681R resistors
NO WOBBLE Perfect control to 1MOhm
1. Same 100k dual gang pot
2. 1k resistor as last experiement
3. 2 681R resistors, 1 for series and one for shunt
NO WOBBLE Perfect control to 28.4k
1. Same 100k dual gang pot
2. 1k resistor as in last experiment
3. 4 681R resistors, 1 for each LDR
NO WOBBLE Perfect control to 59k
SOOOOooooOOO
In this experiment I used 20VDC going to a LM7805 with .33uf and .1uf ceramic caps on the regulator. I used no parallel resistor as I have suggested in the past and I dont know what the effect would have been.
There is my data. Take it for what its worth but my recommendation today is to use dual gang pots for stability and to get the best use out of the LDRs.
Next I will do the same experiments with the original Lightspeed circuit and the same 4 LDRs I just tested. I have 100R resistors in place to test but its time to make dinner and this sometimes takes up to much time.
Interesting stuff.
Uriah
Looks like I forgot to do the 500k single gang at this setting
1. Same two pots
2. No 1k resistor
3. 2 681R resistors - 1 for shunt and 1 for series
Will test this setting when I go about the next series of experiments.
Uriah
1. Same two pots
2. No 1k resistor
3. 2 681R resistors - 1 for shunt and 1 for series
Will test this setting when I go about the next series of experiments.
Uriah
Just for giggles try putting all 4 LDRs in any of these circuits. Put DMM leads on one LDR. Put it to any setting. Remove any single one of the other 3 LDRs. Watch the resistance. Now remove another and another. Interesting.
No I am not telling right now 🙂 Its nothing fantastic its just something I cant explain and really dont have a guess for. The change is dramatic but the voltage change doesnt indicate this drastic change and if it was all based on current why doesnt it happen when you remove the second and third!?
Uriah
No I am not telling right now 🙂 Its nothing fantastic its just something I cant explain and really dont have a guess for. The change is dramatic but the voltage change doesnt indicate this drastic change and if it was all based on current why doesnt it happen when you remove the second and third!?
Uriah
Above, when I was testing the 100k dual pot and said "as instructed by George" I should have elaborated and said that the pot was wired up exactly as George had intended and has instructed. I did not mean to say that George has instructed anyone to use the 1k in series but it sounds like that when I read it back to myself.
Uriah
Uriah
Hey Uriah
I will be putting mine together Monday. I have the original circuit in mind with the exception of a 500k dual and only 1 trimmer. I will be using Salas' 6 LED shunt style PS. I'll let you know what I get for measurements.
I will be putting mine together Monday. I have the original circuit in mind with the exception of a 500k dual and only 1 trimmer. I will be using Salas' 6 LED shunt style PS. I'll let you know what I get for measurements.
Waiting for this set, as it is the most similar to my actual posted setup.
But your similar test with 100k shows a minimum wobble to be a single gang and only 2 resistors.
Anyway, nice to see LSA configurations are not so obvious and quite equivalent among them as illustrated until now and before your tests...
Very nice work and very interesting!
Regards,
Gianni
Hey Uriah,
Your observation of single gang pot was exactly the odd symptom that I mentioned before. In my tests, the series resistance always increased as the pot turned, and the impedance curve looked a lot better/smoother.
When you test the 100R in series each LDR's LED, can you also tested how much current consumed when the pot is in the end positions? Given the high sensitivity of your LDR's, I suspect they may draw over 25ma.
After many experiments, I am very convinced that there is general guideline to build the LSA, but there is no one size fits all. However, there are always ways to make a set of LDR work to your liking. In fact, by varying the pot and the resistor value, you can tune the LSA to certain impedance.
Bill,
I am interested in Salas's shunt PS as well. Please let us know your result. Heads up, in normal listening scenario, the shunt will be burning all the current as the LSA will only draw micro-amp. Plan for 50ma total should be more than enough.
Your observation of single gang pot was exactly the odd symptom that I mentioned before. In my tests, the series resistance always increased as the pot turned, and the impedance curve looked a lot better/smoother.
When you test the 100R in series each LDR's LED, can you also tested how much current consumed when the pot is in the end positions? Given the high sensitivity of your LDR's, I suspect they may draw over 25ma.
After many experiments, I am very convinced that there is general guideline to build the LSA, but there is no one size fits all. However, there are always ways to make a set of LDR work to your liking. In fact, by varying the pot and the resistor value, you can tune the LSA to certain impedance.
Bill,
I am interested in Salas's shunt PS as well. Please let us know your result. Heads up, in normal listening scenario, the shunt will be burning all the current as the LSA will only draw micro-amp. Plan for 50ma total should be more than enough.
The wobble is weird. Lets say that I said wobble was from 8k-10k. It would have done something like this.... 8k..8.5k...8k...8.5k..9k..10k..9k..8k..9k..10k.. and then on being fine.
Most tests I got wobble in two places. Lets guess at why.
First I think that I always got two wobbles but may not have seen the second one since the value may have been increasing so fast that I flew right by it.
Second I wonder if there is a certain divisible AW/WB that creates a fight between the two sides of the pot or at which the LEDs start to fight over current as Gianni suggests.
Could it just be my pots, I dont think so because you guys are getting all the other symptoms and maybe you are getting the wobble to.
Yesterday I did two 100k tests with dual gang pot
Dual 100k pot
1. Dual 100k pot
2. 1 100R resistor in series with each LDR
Perfect control to 5.7k
1. Dual 100k pot
2. 1k resistor
3. 1 100R resistor in series with each LDR
Perfect control to about 28k then very quickly to 100k and then again quickly to 368k at the end of rotation.
I think you are correct Fred and that had entered my mind as testing these. You can find a perfect value to 'tune' your overall impedance. It will be very low, under 100R. Someone in the original Lightspeed thread already found this to be true and was mentioning 20-30R to give him more use of the full rotation of the pot.
I had a bunch of 1k and 681R resistors and paralleled 1, 2, 3, and 4 of them. Overall impedance dropped dramatically with a 100k dual gang pot with the resistors stacked in parallel to each other but in series with the 5VDC and the control pot. Also I think if I had graphed it there would have been a soon predictable curve. So what can we do with this at home? We can make a rotary switch with maybe 6 values of resistors and switch them in and out of series with the 5VDC. Now we have adjustable impedance. Our LDR attenuator can work no matter how low our control pot is in value and no matter how low our LDRs measured. Good stuff to know and something I have been looking for an answer to for over a year. How to very simply control impedance. Now the task is to try it and to see how linear this impedance is. When we throw a resistor in series and get overall 40k impedance does that stay similar through rotation of the dual gang pot or does it dance all over?
Gianni, while I may have gotten upset over what you wrote and the way I interpreted it, you have certainly pushed me to learn more in the last couple days and I appreciate that greatly.
Lets keep at it 🙂
Uriah
Most tests I got wobble in two places. Lets guess at why.
First I think that I always got two wobbles but may not have seen the second one since the value may have been increasing so fast that I flew right by it.
Second I wonder if there is a certain divisible AW/WB that creates a fight between the two sides of the pot or at which the LEDs start to fight over current as Gianni suggests.
Could it just be my pots, I dont think so because you guys are getting all the other symptoms and maybe you are getting the wobble to.
Yesterday I did two 100k tests with dual gang pot
Dual 100k pot
1. Dual 100k pot
2. 1 100R resistor in series with each LDR
Perfect control to 5.7k
1. Dual 100k pot
2. 1k resistor
3. 1 100R resistor in series with each LDR
Perfect control to about 28k then very quickly to 100k and then again quickly to 368k at the end of rotation.
I think you are correct Fred and that had entered my mind as testing these. You can find a perfect value to 'tune' your overall impedance. It will be very low, under 100R. Someone in the original Lightspeed thread already found this to be true and was mentioning 20-30R to give him more use of the full rotation of the pot.
I had a bunch of 1k and 681R resistors and paralleled 1, 2, 3, and 4 of them. Overall impedance dropped dramatically with a 100k dual gang pot with the resistors stacked in parallel to each other but in series with the 5VDC and the control pot. Also I think if I had graphed it there would have been a soon predictable curve. So what can we do with this at home? We can make a rotary switch with maybe 6 values of resistors and switch them in and out of series with the 5VDC. Now we have adjustable impedance. Our LDR attenuator can work no matter how low our control pot is in value and no matter how low our LDRs measured. Good stuff to know and something I have been looking for an answer to for over a year. How to very simply control impedance. Now the task is to try it and to see how linear this impedance is. When we throw a resistor in series and get overall 40k impedance does that stay similar through rotation of the dual gang pot or does it dance all over?
Gianni, while I may have gotten upset over what you wrote and the way I interpreted it, you have certainly pushed me to learn more in the last couple days and I appreciate that greatly.
Lets keep at it 🙂
Uriah
Well,
It works
I put a 1k trimmer in series and turned the control pot all the way. Impedance was 10k. I need another set of clips for my other DMM. I ordered a few days ago. I would like to watch the resistance change on both series and shunt.
I could dial in my impedance. I dialed to 10k and then checked the trimmer and it was 22.22R This is on a set of LDRs that tested in matching at 2047R with 100k inbetween them and 5VDC. When I put them in together into the original Lightspeed circuit they all increase by nearly threefold in resistance simple because of the circuit they are in. Matching is still good at this point. Then I add in the 22.22R and we jump to 4.5X their matched resistance at 100k.
Uriah
It works
I put a 1k trimmer in series and turned the control pot all the way. Impedance was 10k. I need another set of clips for my other DMM. I ordered a few days ago. I would like to watch the resistance change on both series and shunt.
I could dial in my impedance. I dialed to 10k and then checked the trimmer and it was 22.22R This is on a set of LDRs that tested in matching at 2047R with 100k inbetween them and 5VDC. When I put them in together into the original Lightspeed circuit they all increase by nearly threefold in resistance simple because of the circuit they are in. Matching is still good at this point. Then I add in the 22.22R and we jump to 4.5X their matched resistance at 100k.
Uriah
I hope none of this worries anyone thinking to build this or similar circuits. It still works, just the way it works is surprising us because its not nearly as simple as the circuit suggests. Actually the circuit we are all freaking out about is the same one I am using in my prize possesion at the moment. I will modify it however because I dont like the fact that it goes so high in impedance at any point. But right now its the best sound I have ever had from a pre. Also this circuit is so easy to build that there is no sense in 'waiting' for any of us to find the perfect circuit and announce it. George has already done that, build it that way and be happy 🙂 and if you want to tweak later then see what we are talking about and put it together on proto board and play as well. Its fun, its addictive, its the best thing since sliced bread and stereo.
😀
😀
Fred,
I dont get it. I tried what you suggested. No series resistor. Only control pot and 100R resistors. Put the probe on ground and the other after the resistor and before LED positive input. mA are from .001 to .004 and are all over the place, nothing linear about the way they change. Then I switched to voltage. Voltage changes in a predictable manner from 1.98 to 1.48VDC. So I guess I dont know what the heck is going on here.
I tried one of my single gang pots and got the same result.
Used series resistor and also removed it. Same result.
You guys need to try this and see what is going on. Voltage and amperage are changing but voltage is predictable.
I need to go to a Houston Audio Society meeting. When I get back I will try with only one LDR and I will try with only 3 LDRs. Remember the weirdness when the 4th LDR is introduced? Lets see what that has to do with current and voltage.
Uriah
I dont get it. I tried what you suggested. No series resistor. Only control pot and 100R resistors. Put the probe on ground and the other after the resistor and before LED positive input. mA are from .001 to .004 and are all over the place, nothing linear about the way they change. Then I switched to voltage. Voltage changes in a predictable manner from 1.98 to 1.48VDC. So I guess I dont know what the heck is going on here.
I tried one of my single gang pots and got the same result.
Used series resistor and also removed it. Same result.
You guys need to try this and see what is going on. Voltage and amperage are changing but voltage is predictable.
I need to go to a Houston Audio Society meeting. When I get back I will try with only one LDR and I will try with only 3 LDRs. Remember the weirdness when the 4th LDR is introduced? Lets see what that has to do with current and voltage.
Uriah
Yes, it has me wondering.
I am considering using this in a tube preamp which requires a
250Kohm stepped attenuator.
What is the in/out resistance of the ldr control?
Hi Uriah,
Thanks for trying and sorry for not being clear.
I meant to measure the voltage across the 100R and use it to compute the current being consumed. Since the pot at the extreme positions, the circuit will be similar to
5VDC ===> 100R ===> LDR ===> Ground
Measure the voltage across the 100R above. From many of my LDR's, I could measure up to 2.92VDC across. This implies 29ma passing through the LDR which is above the max current of 25ma!! Since your LDR's are very sensitive, I wonder there will be any different from mine.
Even though 100R is recommended by George, I found this value is not enough to protect both over current and over voltage. Quite honest, I wouldn't use anything less than 200R for the LDR's well being. FWIW, at 6.9ma, many of my LDR's give approx 50R resistance. There is no need to draw any current above 10ma.
Thanks for trying and sorry for not being clear.
I meant to measure the voltage across the 100R and use it to compute the current being consumed. Since the pot at the extreme positions, the circuit will be similar to
5VDC ===> 100R ===> LDR ===> Ground
Measure the voltage across the 100R above. From many of my LDR's, I could measure up to 2.92VDC across. This implies 29ma passing through the LDR which is above the max current of 25ma!! Since your LDR's are very sensitive, I wonder there will be any different from mine.
Even though 100R is recommended by George, I found this value is not enough to protect both over current and over voltage. Quite honest, I wouldn't use anything less than 200R for the LDR's well being. FWIW, at 6.9ma, many of my LDR's give approx 50R resistance. There is no need to draw any current above 10ma.
I didn't understand...how can you measure the current with a probe to ground? Written as it is, it seems to me that DMM is in parallel not in series.
Happy to see that there was a "complicated" story behind the LSA, never told before... 🙂🙂🙂
Uriah,
I think we will throw everything in the trash when you'll match in CCS and we will control with a lm334.
No more overdriven pots (it will only control lm334 adj pin), no resistors, no interferences, just a wonderful, stable and reliable LSA!!!
Gianni
I think we will throw everything in the trash when you'll match in CCS and we will control with a lm334.
No more overdriven pots (it will only control lm334 adj pin), no resistors, no interferences, just a wonderful, stable and reliable LSA!!!
Gianni
I use mostly tube gears and haven't had much success with the LSA. I can flag a couple reasons (in my case):
1. LDR's are very sensitive to temp, and tube gears are hot. I don't have
good material to isolate the LDR's from the heat. They are just not the
same thing when place a couple free from a 75wpc tube amp ...
LSA as well any other passive preamps don't like long cable. So, I
can't place it far enough from the heat source.
2. LSA wants low output impedance from the source. Neither my
tube dac nor the Jolida JD100A satisfy this requirement, not even close.
I do have a few couple sand Dac - dpa, Adcom, and a ARC, but they don't
sound as good as the tube counter parts.....
I kind of knew the above before I decided to try the LDR's. It is cheap by comparison to other gears. So far, I still prefer my active tube pre than LSA. Part of that is snergy of various gears, and the other part is the freedom of changing source and amps. I will continue to tweak and find a way to use the LDR's.
IMHO, it is not very likely that you can make the LSA to be a 250K pot. If you are able to tweak it, I am not sure Uriah match anything in the high up range.
The Lightspeed could for sure replace a 250k but it would be a hard thing to match LDRs for. They get quite unpredictable at higher than around 25k. The holy grail here is when one of us programs a microcontroller and actually shares the code and the circuit. Then we can have our cake and eat it to.
I have to say that I have not experimented with different sources driving the Lightspeed. Total I have heard 4 different sources through it. All sounded wonderful.
I dont have issues with long intereconnects meaning 3ft from cd to LSA and 3 more ft to amp. No problem.
So, all in all I would not try to replace a 250k pot but I would build the LSA circuit and stick a buffer after it and have the best sound possible. I have not heard a preamp that touches the LSA at all. Its my opinion of course but I have had countless guys email me telling me how its the best they heard, many replaced their Prometheus TVC and a few even tell of tears because the music was so incredibly more transparent through the LSA. Its the truth and for $38 I am not about to start selling snake oil. Its flat out the best I have ever heard. It drove a Wavelength 300B, I forget SE of PP or SET, but I think SET. Anyway it was the most beautiful combo I have ever heard and please dont ask me specs on the amp. I dont know.
Fred, I will try what you meant with 100R.
Gianni, yes LM334 is the way it needs to eventually go if I dont get some sudden blessing by God and all of a sudden learn how to program microcontrollers.
Uriah
I have to say that I have not experimented with different sources driving the Lightspeed. Total I have heard 4 different sources through it. All sounded wonderful.
I dont have issues with long intereconnects meaning 3ft from cd to LSA and 3 more ft to amp. No problem.
So, all in all I would not try to replace a 250k pot but I would build the LSA circuit and stick a buffer after it and have the best sound possible. I have not heard a preamp that touches the LSA at all. Its my opinion of course but I have had countless guys email me telling me how its the best they heard, many replaced their Prometheus TVC and a few even tell of tears because the music was so incredibly more transparent through the LSA. Its the truth and for $38 I am not about to start selling snake oil. Its flat out the best I have ever heard. It drove a Wavelength 300B, I forget SE of PP or SET, but I think SET. Anyway it was the most beautiful combo I have ever heard and please dont ask me specs on the amp. I dont know.
Fred, I will try what you meant with 100R.
Gianni, yes LM334 is the way it needs to eventually go if I dont get some sudden blessing by God and all of a sudden learn how to program microcontrollers.
Uriah
So Fred,
I put the leads across the 100R resistor. One on each side. This was with the control pot in place. Again I got the same as I reported.
Just a sec and I will try without the pot,just resistor.... Without pot and with just 100R in series with each LDR from 5VDC I get the same mA as I said before.
I get 4.96VDC from the LM7805 and then, without the pot, I get 2.8V at the regulator side of each set of two resistors. On the opposite side of the resistor I get 2.1VDC.
Fred can you try this out and see what happens? Dont assume what should happen, just try it. You have lots of spare LDRs right?
Uriah
I put the leads across the 100R resistor. One on each side. This was with the control pot in place. Again I got the same as I reported.
Just a sec and I will try without the pot,just resistor.... Without pot and with just 100R in series with each LDR from 5VDC I get the same mA as I said before.
I get 4.96VDC from the LM7805 and then, without the pot, I get 2.8V at the regulator side of each set of two resistors. On the opposite side of the resistor I get 2.1VDC.
Fred can you try this out and see what happens? Dont assume what should happen, just try it. You have lots of spare LDRs right?
Uriah
Okay, I got my new DMM 2 days ago. Pretty thrilled with it but when I went to measure the mA I forgot to switch my leads over to the current reading jack. Dumb.
Anyway, got it sorted and it looks like I am running about 102mA and this is with the 4 resistors and the 4 LDRs.
So I have a wire going to the end of each pair of resistors. So one wire to two resistors and each resistor to an LDR. This formation twice.
I put the probe on the junction of the wire and resistors and then on the other side of one of the two resistors. At this point I am reading 104mA. When I remove an LDR not associated with that resistor I get a jump to 108mA-112mA. When I remove the associated LDR current goes to 0. When I put it back it jumps up to 200mA and then cools down over 60-90 seconds to 104mA.
At this point LDRs read 24, 27, 40, 54 Ohms.
I remove one LDR it jumps like I stated but it does this with the removal of each LDR. A jump in current.
Lets try a pot...
Okay, current can change from .014mA to 200mA. Everytime I go to either extreme it jumps to 200mA then it slowly decreases when pot is left at that extreme. Same as with no pot but removing the LDR and replacing it.
I didnt believe this was happening. Tried a different DMM. Same results.
So Voltage AND current vary.
Uriah
Anyway, got it sorted and it looks like I am running about 102mA and this is with the 4 resistors and the 4 LDRs.
So I have a wire going to the end of each pair of resistors. So one wire to two resistors and each resistor to an LDR. This formation twice.
I put the probe on the junction of the wire and resistors and then on the other side of one of the two resistors. At this point I am reading 104mA. When I remove an LDR not associated with that resistor I get a jump to 108mA-112mA. When I remove the associated LDR current goes to 0. When I put it back it jumps up to 200mA and then cools down over 60-90 seconds to 104mA.
At this point LDRs read 24, 27, 40, 54 Ohms.
I remove one LDR it jumps like I stated but it does this with the removal of each LDR. A jump in current.
Lets try a pot...
Okay, current can change from .014mA to 200mA. Everytime I go to either extreme it jumps to 200mA then it slowly decreases when pot is left at that extreme. Same as with no pot but removing the LDR and replacing it.
I didnt believe this was happening. Tried a different DMM. Same results.
So Voltage AND current vary.
Uriah
Yup, this should be the case. The goal is to see the 100R is enough to protect the LDR's when the pot is at the extreme positions which the pot is effectively absence.
Bingo, I already tried this and just wanted to double check with you to see the very sensitive LDR would behave differently. It doesn't!! BTW, my reading was approx 2.97V and 2.0V respectively. When there is 2.8V across the 100R, there is 28ma passing through it, I=V/R. This means the LDR is pulling 28ma, no good, exceeding the max current of the LDR. So, avoid to turn the pot all the way down or up if 100R is used!!
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