• These commercial threads are for private transactions. diyAudio.com provides these forums for the convenience of our members, but makes no warranty nor assumes any responsibility. We do not vet any members, use of this facility is at your own risk. Customers can post any issues in those threads as long as it is done in a civil manner. All diyAudio rules about conduct apply and will be enforced.

Silonex LDRs for Lightspeed Attenuator

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Re: LDR SHIPPING UPDATE

udailey said:
I have been without air conditioning for now 3 days. This past weekend I was supposed to do my last test for matching. They say they will get it fixed tonight. I cant test when the temp is so hot. It throws off the matching. I need it to be 75F in here to match all other tests and I need it to be a stable temp.
WHat does this mean? It just means that it will put shipping back a few days. I need a full day to do the testing so that means I need Saturday or Sunday. I will, during this week, get all boxes labeled and ready to ship. So then I can match on Saturday and ship midweek next week.
Sorry guys but it was out of my hands. Every time they get the AC fixed it triggers the huge breaker it is on. They had to go buy a new compressor so they tell me tonight it will work.
How do you think it must be in an apartment with no AC in Houston? LOL Not real cool. Lots of going to the mall and swimming to keep cool.
Hope you can all understand. Will be doing everything ASAP.
Uriah

Uriah - are we cool now??:hot: :hot:

Alan
 
Alan,
Got it fixed last night. Now we are settled back in at 75F. When its 100+ outside and the AC goes...... yeah. I dont want to go back to that.



WCT
Let me get done with this buy. I will announce how many I have left at that point. So watch this thread. I will announce that within a week. I dont want to sell out as that would leave someone a little upset.

I think I will keep matching as long as you guys keep wanting to try the circuit. I am getting interested in new ways to control them simply because its the only thing you can really tweak on this circuit other than adding a buffer.
 
Hey Now!
I am fortunate enough to have been able to stash a little cash away and would be interested in whatever I would need for an SE attenuator. So let me know if / when any open up.
Hope the AC doesn't conk out again on you, I can sympathize my office has been a steady 86F until just last week when they installed a stand alone unit, whew!
 
Hi, Georges MKII is the same as the circuit shown in my diyAudioProjects page. The only thing different is the pot used is a single instead of a dual. Yeah you could do it that way. I have NO idea why it would be any different and i dont think it would. So for those wondering, you could use a single log pot and feed 5VDC to the wiper then take output voltage from the other two pins. This would be the same as using a dual log pot. Make sure the pot can handle more than one half watt.
You will need a 500k pot. A 100k pot will give you an overall LDR impedance of about 1.2k and you wont like that to much :) Use 500k with these LDRs.
If I do another purchase and sale of matched LDRs I might be recommending 100k again or 300k who knows. Depends on how the LDRs are when I measure them. This particular batch matches beautifully but their resistance really ramps up slower than the previous. However they are more stable at higher resistance than any others have been so we can get nice cooperation from them with each one giving around 10k + at 400k in series with 5VDC.
Uriah
 
tinitus said:
I have found cheap Cermet linear mono pots with 500k

I can also get various small bevel gears from same place

Those could be arranged to work with the motor, and maybe to adjust balance

Hi Tinitus,

Is yours a double or single gang pot? I can only find 500K linear single gang locally. Looks like I will need to try & see if George's single log pot circuit will work for me.
 
Lets assume you use a dual gang pot. You have on the first gang 3 points to solder to. One is the wiper. So lets call them 1 W 3 and on the second gang we have the same so lets call them A W2 C.
You would solder W and 1 together and you would solder W2 and C together. These 2 new points are where you take power from. You would give the pot 5VDC at 3 and A.
So can you do the same thing with a single gang pot? Yep. Lets assume points X W Y. You simply give the wiper (W) the 5VDC and take the resulting power from X and from Y. X and Y are NOT soldered together. By giving the wiper 5VDC we essentially turn the pot into two different variable resistors but they are not independantly variable. One varies when you adjust the other. If its a 500k pot then when you turn it to halfway both sides are 250k but when you turn one side to 125k the other is 375k. One half supplies the Shunt LDRs with power and the other side supplies the Series LDRs with power.

Here are some from Mouser

MOUSER POTS

And one from NEWARK

And APEXJR

Uriah
 
I am decidedly indecisive! :)
I think the bourns from ApexJr is the way to go for a single gang pot. I see no reason that a single gang wont work. I have only used dual gang and got my dual gangs from Mouser.
PN 313-2420F-500K
But if you cant find a dual try a single. It should work the same. Think about the schematic of using a dual and think about the schematic of a single and think how the electricity flows through it. These should be the same for our purposes.
Uriah
 
500k Log Pots

Guys/Gals,
A few people have expressed concern, not being able to find 500k pots. Hadnt thought this would be a problem but I dont want you guys to have problems.
I just bought 100 500k audio taper pots from Mouser. Single gang as I could not find anything with a decent price on dual gang.
I will include one with every order. No charge.
There is a caveat with this free potentiometer. I have not used a single gang pot. I think it will work fine. If it gives you trouble please try to find a dual gang pot OR get another single gang and use two pots.
Cheer up gang, these are fun, easy, and sound wonderful and are right around the corner. I think you will be able to implement the circuit just fine with the single gang pot. Dont forget you will need some sort of trim pot and when we are running a 500k pot for control you will need something pretty serious to correct even the smallest stray traveling LDR. I previously suggested 25k multiturn and still think that will work fine. You could probably get away with 10k single turn, but I like the multiturn pots for fine tuning. On my Lightspeed I use a 5k multiturn with a 100k pot because I got my LDRs from a previous batch. I can "set it and forget it" as I suspect you will be able to do as well if you need to tune the balance. I like having the trimming pot as a chassis mount so it is accessible from the outside of the chassis.
Uriah
 
Including a 500k pot is a nice consolation.

I would still like to make this a remote controlled unit so a couple questions regarding the pot change:

Firstly, since the pot simply adjusts the voltage to the devices, could adjusting the voltage up or down slightly make the use of the dual 100k feasible?

Also, I found these 500K "Alps" pots on ebay and think I can simply swap out the 100Kx2 on my motorpot for one of the 500Kx2. These are not shown on any ALPS JAPAN data sheet I can find so Im assuming they are bogus. But since quality isnt an issue, they might be fine. Anyone have any experience with these and know if they are identical copies or not?

http://cgi.ebay.com/ALPS-RK27112-Po...tem3a510a85ae&_trksid=p4634.c0.m14&_trkparms=|293%3A1|294%3A30

amt
 
I wish I had more time to run some tests. I have been experimenting with different ways to control them. I you could lower the voltage to around 2.5v but I have not tested them at this voltage so I am not sure if they would track the same in measurements. This would be your experiment at this point. You can also control them with a 100k pot and LM334 but I dont think they will match anymore. However these are a few possible solutions.
The ebay pots. I have had people say that they are in general knock offs but that they use individual resistors rather than a carbon track. Thats all fine and dandy. I dont know if you could use it in your remote.
After I get done with shipping these I will be back to experimenting and we could work together if you like, sharing info on what does and doesnt work. I think its possible to find an LM334 solution, but until I mess with it some more I dont know.
Actually I am positive about lM334 but I am not sure if a pair matched the way I am matching will then remain matched at different voltages or controlled by current vs voltage, etc. I will be trying to match more using LM334 and will be quite pleased if that works out well.
100k is definitely NOT going to give you good results with these LDRs if you follow the circuit as it is now. You will end up with to low impedance.
Wish I could have better solution for your question, but right now my only guarantee is using a 500k will work well.
 
Salut U

Hmm - need some help here, please. I'm planning on using Paul's VCCS (bought the PCBs) - so from what I read there could be matching problems if the LDRs are driven from a current rather than voltage source - is that right? Also, if I continue with the VCCS (boards already populated and awaiting arrival of the LDRs) does the change to a 500k pot have an influence on Paul's design?

Last one - as you're starting current matching experiments would it be possible to check mine before shipping, please?

Merci.

Vernon
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.