Search found 91 matches

by foxmiles
Thu Dec 04, 2014 2:05 pm
Forum: Brainstorm
Topic: Arduino/ATMega based Digital Soldering station
Replies: 56
Views: 46135

Re: Arduino/ATMega based Digital Soldering station

Wow, It's been ages since I've been here. got the urge to finish this project again, so here's another polynomial, this time one that hopefully works. I think the other one didn't, at least not on an Arduino (variable size problems (needed 64bit floats?), also not the right coefficients anyway, not ...
by foxmiles
Sun Nov 17, 2013 3:16 am
Forum: Brainstorm
Topic: Arduino/ATMega based Digital Soldering station
Replies: 56
Views: 46135

Re: Arduino/ATMega based Digital Soldering station

Math (or at least algebra) is not my specialty, in fact it's a pretty big weak spot that I'm working on. I've been looking into ways to convert the reading from the adc to MV and then to degrees C. So far I've got preliminary compensation code: mv = reading*(4950/1023)-136-80; //reading*(vcc/1023)-o...
by foxmiles
Fri Nov 15, 2013 3:49 am
Forum: Brainstorm
Topic: Arduino/ATMega based Digital Soldering station
Replies: 56
Views: 46135

Re: Arduino/ATMega based Digital Soldering station

Here's a very preliminary first draft of my Rev B schematic. It wouldn't let my upload a pdf, so here's a hi-res jpg: Solder station.jpg A 1k(r4) and 100k(r5) combo seems to work good for me. It gives about 100x gain. (10k and 1M would be the same gain) I've messed with the board design a bit and ha...
by foxmiles
Thu Nov 14, 2013 9:07 pm
Forum: Brainstorm
Topic: Arduino/ATMega based Digital Soldering station
Replies: 56
Views: 46135

Re: Arduino/ATMega based Digital Soldering station

OK, I had a chance to build it on a breadboard and take some measurements. Here's what I found (so far) 1. With a 5v supply the lm358 saturates around 3.5v (vcc-1.5v), the output range is about 0-3.5V. For some reason I thought it was 0.5-4.5v. No idea why I thought that. My 330K resistor makes it s...
by foxmiles
Sat Nov 02, 2013 2:32 am
Forum: Brainstorm
Topic: Arduino/ATMega based Digital Soldering station
Replies: 56
Views: 46135

Re: Arduino/ATMega based Digital Soldering station

Cool, I think I'll build it up on a breadboard when I have chance. It'll be at least a week though. as far as inaccuracies when applying current it could be inductance. We're measuring very small voltages, so even a little EMI could cause problems. One suggestion I have: you mentioned a bouncing eff...
by foxmiles
Tue Oct 22, 2013 1:55 am
Forum: Brainstorm
Topic: Arduino/ATMega based Digital Soldering station
Replies: 56
Views: 46135

Re: Arduino/ATMega based Digital Soldering station

Sorry I didn't reply, was out of town for a bit. I don't know what's wrong (or different) with my circuit, I'll play with it when I have a chance, but I've got some stuff to finish up before it gets cold here. I wouldn't worry too much about the temperature compensation thing at the moment, especial...
by foxmiles
Fri Oct 04, 2013 12:42 pm
Forum: Brainstorm
Topic: Arduino/ATMega based Digital Soldering station
Replies: 56
Views: 46135

Re: Arduino/ATMega based Digital Soldering station

I have made the "hefty" 5A trafo as I said earlier Cool! I've never made a transformer. Sounds like it will do the trick! with an ideal opamp output, 0-5V for. would give a reading 0-1023? is that it? Yep, that's it. Just multiply by 4.88 to get a MV reading (5000MV / 1024Steps). As a side note you...
by foxmiles
Fri Oct 04, 2013 1:32 am
Forum: Brainstorm
Topic: Arduino/ATMega based Digital Soldering station
Replies: 56
Views: 46135

Re: Arduino/ATMega based Digital Soldering station

I'm Steve, I'm working with Tom on this (I'm his brother). A few thoughts: As long as the opamp is supplied from the 5v rail and ground there is no need to worry about it's output exceeding 5v. The lm358 isn't a rail to rail opamp, so it will never go all the way to 0 or 5v, it will be somewhere in ...
by foxmiles
Thu Oct 03, 2013 5:26 pm
Forum: Brainstorm
Topic: Arduino/ATMega based Digital Soldering station
Replies: 56
Views: 46135

Re: Arduino/ATMega based Digital Soldering station

Yea, I've considered a thermistor on the board, it's probably the way to go, the internal one would be room temp on boot and should stay within ~10C, but it requires some work to read, so I might just read it once on boot and assume it will stay close enough (it would improve the accuracy without ad...
by foxmiles
Thu Oct 03, 2013 3:40 am
Forum: Brainstorm
Topic: Arduino/ATMega based Digital Soldering station
Replies: 56
Views: 46135

Re: Arduino/ATMega based Digital Soldering station

Hi dearangelo, I'll give you the info I have, though I haven't had time to do much more on it than what was in my last post. which resistor combo would give a "readable" output so to be able to display temps from around 0C or 32F. Honestly I don't know, I would grab a k-type thermocouple chart and p...