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If in fact the R1 resistor is 500 ohms a 5K pot would give you 1.5 volts to 13.53 volts . A 1k pot would give you a range of 1.5 volts to 3.69volts .
These modules come in a few different max outputs that i have seen on Ebay. 20 volts 25 volts 35 volts 40 volts. The formula is ( R2 divided by R1 +1 ) then multiply that number by 1.23 and that will give you the high end output voltage. When the pot is dialed to no resistance you get the low voltage of 1.5. Anyways the R1 resistor value is critical in the calculation of the proper value pot. If all the voltages above use a 10k pot the R1 resistor value is going to be different.
Kinda, but it could very well just be a pot/trimmer using all three leads.
Here's a typical R1/R2 voltage divider using just a pot.
Dumped all the resistors from the original design and went with only the pot that now is both R1 and R2.
just to add to the above a bit maybe make it easier to understand
We know bj43 's reg has a top end output of 25 volts we also know it has a 10k pot. so we take the formula (R2 divided by R1 +1 ) x 1.23 = output voltage. R2 the Pot is 10000 ohms. If we plug in 500ohms for R1 we have 10000 / 500 = 20 , 20+1 = 21 , 21 x 1.23 = 25.83 output voltage.
Now the lm2596's i am getting have a output max of 35 volts. For the pictures i can also tell they come with a 10k pot. so if i plug in 360ohms for R1 i get , 10000 / 360 = 27.777 , 27.77 + 1 = 28.77 , 28.77 x 1.23 = 35.39 output volts
ok thats enough math for me today, I swear i hear Samual Adams telling me there is a boston lager with his name on it , but assures me it is for me , waiting on me at the beer store .
We know bj43 's reg has a top end output of 25 volts we also know it has a 10k pot. so we take the formula (R2 divided by R1 +1 ) x 1.23 = output voltage. R2 the Pot is 10000 ohms. If we plug in 500ohms for R1 we have 10000 / 500 = 20 , 20+1 = 21 , 21 x 1.23 = 25.83 output voltage.
Now the lm2596's i am getting have a output max of 35 volts. For the pictures i can also tell they come with a 10k pot. so if i plug in 360ohms for R1 i get , 10000 / 360 = 27.777 , 27.77 + 1 = 28.77 , 28.77 x 1.23 = 35.39 output volts
ok thats enough math for me today, I swear i hear Samual Adams telling me there is a boston lager with his name on it , but assures me it is for me , waiting on me at the beer store .
Is that for the math or the beer?
Java
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These 70 year old fingers don't solder anything smaller than 1/4 inch. lol. Thanks for all the math, cool...
NTE Electronics NTE 500-0103-BU 63P-T607-502 TRIM 5K OHM<br><a href="http://www.arcade-electronics.com/nte_electronics.aspx">NTE Electronics Selection Page</a> - 63P T3 Style series (NTE 500 series) - Arcade-Electronics.Com - Detail
Probably with my limited soldering ability this would be the best improvement for now.
Probably with my limited soldering ability this would be the best improvement for now.
Using Java's math, couldn't you get the same result with a 200ohm pot & a 10 ohm resistor? If I understand the discussion correctly, you wouldn't have the 'twitchiness' in the vaping zone...
NTE Electronics NTE 500-0099-BU 63P-T607-201 TRIM 200 OHM<br><a href="http://www.arcade-electronics.com/nte_electronics.aspx">NTE Electronics Selection Page</a> - 63P T3 Style series (NTE 500 series) - Arcade-Electronics.Com - Detail
NTE Electronics NTE 500-0099-BU 63P-T607-201 TRIM 200 OHM<br><a href="http://www.arcade-electronics.com/nte_electronics.aspx">NTE Electronics Selection Page</a> - 63P T3 Style series (NTE 500 series) - Arcade-Electronics.Com - Detail
Replacing the mini R1 on these boards is way past my soldering ability...
Me too. But... one of my in-laws is giving me lessons. First he lets me muck it up, then he shows me what I should have done, and finally has me do it again myself. I've only got a cheesy Radio Shack pen, while he has a whip-... Hakko soldering station. World of difference. He's keeping an eye out for an old Weller for me on the cheap. Says they'll do pretty much anything I need, and that parts are available for even the old ones.
I just looked at my blue board 2596 and R1 is 471ohm.
I would assume that BJ's "IEE" is actually an upside down 331.
I would assume that BJ's "IEE" is actually an upside down 331.
Not my math it is from the data sheet. Really R1 should be a fixed resistor between 240 ohms and 1.5 k ohms to keep noise out of the feedback pin. At least thats what the data sheet says. But as WillyB pointed out you could run just a pot on the reg.But it should give you the full range of the reg 1.5 to 40 volts. It could also be unstable at certain voltages due to the varying resistance of R1. I am strickly going off the data sheet for my calculations doesnt mean the designer of the circuit did the same thing.
Could very well be 331.
Actually that reading was not from the board I am working on but from a new smaller green board without the meter. These have an output of 35 v
http://www.ebay.com/itm/LM2596-DC-D...022?pt=LH_DefaultDomain_0&hash=item20c3487876
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Should be somewhere around there. But Specs on these chips are not always spot on. I just got a chip today from China ( not the LM2596's they are still not here ) it is supposed to have a adjustable output of 3 to 25 volts. Real life it went from 5 volts to 17.3 volts. Just modified it to go down to 3.2 . So i guess you cant really rely on these sellers to put in the correct specs all the time. Does your chip really go down to 1.5 volts? Since it is a led Model i wouldn't take it over the 25 volts might just fry the LED. I guess really all you can do is slap a 3k pot on that joker and see what she does.
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