#robotics Logs
Feb 12 2012
#robotics Calendar
00:08 XSerpentX oh tom, btw u know that dc motor
00:08 XSerpentX i set up a separate circuit for it
00:08 XSerpentX with the motor controller
00:08 XSerpentX with a load supply of 5v
00:08 XSerpentX and it doesn't turn
00:08 XSerpentX i put 12v on it
00:08 XSerpentX and it goes like hell
00:08 XSerpentX so i'm effed
00:08 XSerpentX well
00:08 XSerpentX unless i put 8x AA in series
00:08 XSerpentX make 12v..and hook that directly up for the main drive motor controler
00:08 XSerpentX then i also regulate that down to 5v for the servo's
00:08 XSerpentX i guess that is ok..
00:08 XSerpentX how long u think 8x AA's will last in an RC car
00:10 XSerpentX i guess i could just pull off the first 4 battiers
00:10 XSerpentX to get my 6v
00:10 XSerpentX so have a +6v wire and a +12v wire
00:11 XSerpentX that makes sence
00:12 yogster hi
00:13 XSerpentX 01010101
00:13 yogster http://i.imgur.com/9nAPb.jpg
00:14 yogster This patient arrive today, any idea what happend?
00:14 yogster guesses?
00:14 yogster clue: wear a seatbelt.
00:16 XSerpentX forget the seatbelt, what about all the electronics that get destroyed in every accident!
00:16 XSerpentX Drunk Driving Kills Electronics!
00:18 yogster another clue: not caused by head slammed into windshield or dashboard.
00:19 XSerpentX he saw 50 cent's penis?
00:20 XSerpentX elephant rape.
00:20 XSerpentX umm..umm
00:20 XSerpentX battery explosion?
00:21 yogster This is an unbelted back seat passenger whose head got whiplashed into the bracket of metal of the seat infront of him after the car was hit by a hard body.
00:21 yogster wear a seatbelt!
00:23 XSerpentX or train as a jedi
00:23 XSerpentX jedi's never wear seatbelts
00:24 jadew where can I find a list of components based on their properties? trying to find a voltage regulator that can go down to 0
00:24 XSerpentX neither do psychers
00:24 XSerpentX um catalogs
00:25 jadew so there's no famous catalog for this kind of search out there?
00:25 XSerpentX there should be..
00:26 XSerpentX but you may have to go to the mfg websites
00:26 XSerpentX i don't think there is a master list
00:26 jadew I see
00:26 XSerpentX or i just haven't found it
00:26 XSerpentX but someone would have had to type in all there characteristics
00:27 XSerpentX and values into a database
00:27 XSerpentX maybe some of the larger component wholesellers
00:27 Triffid_Hunter jadew: regs don't go down to 0 usually. for that sort of stuff you have to provide a negative voltage as the reg's ground
00:27 XSerpentX would do a semi complete list of the brands they carry
00:27 jadew yeah, it looks farnell has a better filter
00:28 jadew Triffid_Hunter, I see
00:28 Triffid_Hunter jadew: http://s.eeweb.com/members/circuit_projects/blog/2012/01/11/LM317-Power-Supply-1326295821.jpg <-- this sort of madness
00:28 jadew yeah, I can't provide negative voltage
00:29 jadew I gave up on using a PC PSU, because I find it dangerous
00:29 XSerpentX really
00:29 XSerpentX how so
00:29 XSerpentX what happened
00:29 jadew too much amps
00:29 XSerpentX really
00:29 jadew it can pop pretty much anything I would play with
00:29 XSerpentX interesting
00:30 jadew apparently the 5v can push up to 40 or more amps
00:30 XSerpentX 30 on mine
00:30 XSerpentX but what brand of ps
00:30 jadew that's 150w
00:30 XSerpentX i wonder why i am so lucky..
00:30 XSerpentX mine is an antec
00:31 XSerpentX i heard shitty psu can do that
00:31 jadew because it doesn't give out particularly high currents, but if you're sweatty enough, I'm sure it can give you a good shock
00:31 jadew *particularly high voltages
00:31 XSerpentX my hands are usually dry
00:32 XSerpentX my resistance is like 5M
00:32 jadew that's not true
00:32 jadew it goes really low once it passes the skin
00:32 XSerpentX u got shocked?
00:32 XSerpentX i guess i should be more careful
00:32 XSerpentX but it's never popped any of my electronics
00:32 jadew I got shoked by touching a usb dongle
00:33 jadew I avoided PSU's till now
00:33 XSerpentX they have surge protection tho
00:33 XSerpentX well unelss it's really shity
00:33 XSerpentX any sign of a power flux and it shuts off
00:33 jadew XSerpentX, that's probably because you made sure to limit the current
00:33 XSerpentX not really
00:33 XSerpentX i desoldered all the wires
00:34 XSerpentX except 1 of each
00:34 XSerpentX 3.3v 5v and 12v
00:34 XSerpentX i only really use the 5v mainly
00:34 XSerpentX i put it to posts
00:34 XSerpentX and each is properly grounded
00:34 jadew I figured, that was my plan as well
00:34 XSerpentX it's an antech ps tho
00:34 XSerpentX so it's high quality
00:34 jadew they can all deliver high amps
00:34 XSerpentX but
00:34 XSerpentX i should add
00:34 XSerpentX i thought it to be defective
00:35 XSerpentX when i took it out of a customers pc
00:35 XSerpentX but for some reason, i tried it again
00:35 XSerpentX and it turned on
00:35 XSerpentX so i tried an experiment with it
00:35 XSerpentX for 5v
00:35 XSerpentX and it worked
00:35 jadew I have a few lying around too
00:35 XSerpentX i did read, using a shitty one is a bad idea
00:35 XSerpentX but it has worked for me for 5 years
00:35 XSerpentX no issues
00:36 XSerpentX but wear ur safety glasses
00:36 XSerpentX n shit
00:36 jadew nice, well, I figure I'll never need more than 1A for the kind of stuff I'm doing, so why take the risk?
00:37 jadew I'm not powering heating devices
00:37 XSerpentX yeah, a fuse is a good idea
00:37 jadew deffinitely
00:37 XSerpentX i should really have one
00:37 Triffid_Hunter jadew: I hang a 7805 off an ATX's 12v rail, works well
00:37 XSerpentX kinda super dum now that i think o fit
00:37 Triffid_Hunter jadew: the reg won't let more than about 1A flow so any mistakes don't cause fire
00:37 jadew Triffid_Hunter, yeah, taht would limit the amps as well
00:37 Triffid_Hunter unless they'd also cause fires from batteries or wall warts
00:38 XSerpentX frig, now i'm nervous
00:38 jadew heh
00:38 Triffid_Hunter jadew: don't need a lot of current in the -ve rail if you want to take an lm317 down to 0, check datasheet for the ground pin current
00:38 Triffid_Hunter jadew: and only need -1.2v, well within the range of a primitive capacitor charge pump like the max232 uses
00:38 jadew Triffid_Hunter, I suppose I should only give it -1.25
00:39 jadew cuz 1.25 it's its referece voltage
00:39 Triffid_Hunter yeah, something like that
00:39 Triffid_Hunter couple of diodes ;)
00:39 XSerpentX how much current can go thru
00:40 XSerpentX a 25 wire
00:40 XSerpentX 25 gage
00:40 jadew Triffid_Hunter, yeah, I think I'm gonna try the diode approach
00:40 Triffid_Hunter XSerpentX: depends on surrounds, google should find you a table
00:41 jadew what's a gage?
00:41 Triffid_Hunter jadew: and capacitor charge pump to generate the -1.3?
00:41 XSerpentX 28 gage wire
00:41 XSerpentX it says .2A
00:41 jadew Triffid_Hunter, no, I figured I could use a few diodes to drop the voltage on the output
00:41 Triffid_Hunter XSerpentX: well keep it below 0.2A then ;)
00:42 XSerpentX well..what if i don't
00:42 XSerpentX what'll happen
00:42 jadew it'll heat up
00:42 Triffid_Hunter jadew: ah that works too, although you lose a lot of accuracy because their forward drop changes with current and temperature
00:42 XSerpentX hmm
00:42 XSerpentX i dunno
00:42 Triffid_Hunter XSerpentX: it'll get warm. too warm and the insulation melts off. much warmer than that and it may catch fire
00:42 jadew Triffid_Hunter, I see
00:42 XSerpentX has'nt tho
00:42 XSerpentX not even warm
00:42 XSerpentX after hours
00:43 Triffid_Hunter XSerpentX: well sure, if you have enough airflow to keep it cool it'll be fine
00:43 Triffid_Hunter XSerpentX: might be a different story when installed in a wall
00:43 XSerpentX hmm
00:52 XSerpentX ya geez
00:53 XSerpentX no idea why i'm still alive
00:53 XSerpentX this thing shoulda ripped a whole thrue my desk
00:53 jadew is it hot?
00:53 XSerpentX not even
00:54 XSerpentX i mean maybe i should check
00:54 XSerpentX maybe i was smart enought to wire it with some kinda safety
00:54 XSerpentX i made it like 2007
00:54 XSerpentX but i don't really remember
00:54 XSerpentX i thought circuits generally just draw what they need
00:55 XSerpentX unless u short
00:55 rue_shop2 the transmission amp works great, off a 5V rail, I get 15V p-p on the antenna
00:55 jadew they do, but a circuit with out a resistor to limit current will draw whatever it can take before it burns out
00:55 rue_shop2 I'm currently transmitting a 555 across the room
00:55 XSerpentX nice
00:55 rue_shop2 but there is something else odd
00:56 rue_shop2 about the way the signal gets mauled
00:56 rue_shop2 I think I see why rc controllers with the 1-2ms pulses work so well
00:57 XSerpentX oh rue
00:57 XSerpentX a while ago
00:57 XSerpentX i noticed on a rc car
00:57 XSerpentX the transmitter send out 5 PWM
00:57 XSerpentX the first was a sync
00:57 XSerpentX the second was drive speed
00:57 XSerpentX the theird was steer
00:57 XSerpentX and i think 4 and 5 were trim
00:57 rue_shop2 its like, to get serial to reliably transmitt, you would need to put a divider on the recieve line and modify the transmitter to send out multiple pulses
00:58 rue_shop2 no they were mt channels
00:58 rue_shop2 er, wrong trim sorry
00:58 rue_shop2 your right
00:58 rue_shop2 the sticks are trimmed mechanically
00:58 rue_shop2 :)
00:59 XSerpentX hmm ya that makes sence
00:59 rue_shop2 at 15V p-p I wonder how far this is transmitting my 33.333Mhz signal
00:59 XSerpentX what else would 4-5 be
00:59 XSerpentX i forget
00:59 XSerpentX it was long ago
00:59 rue_shop2 !assist images
00:59 tobbor Possibly http://eds.dyndns.org/~ircjunk/images
01:00 rue_shop2 http://eds.dyndns.org/~ircjunk/circuits/rc-dec.gif
01:00 rue_shop2 http://eds.dyndns.org/~ircjunk/circuits/rc-enc.gif
01:01 rue_shop2 the 330K does the sync pulse
01:01 rue_shop2 so incredibly flipping simple
01:02 XSerpentX nice
01:02 rue_shop2 iirc you can go up to 10 channels
01:02 rue_shop2 before you eat into the 50hz update
01:03 XSerpentX cool
01:03 XSerpentX what protocal does usb use
01:04 rue_shop2 now you understand how to decode the multiplexed stream on a microcontroller?
01:04 rue_shop2 I think usb operates like rs422, electrically
01:05 rue_shop2 bi-directional differential pair
01:05 Triffid_Hunter more like 485 I think, it's half duplex bidirectional
01:05 Triffid_Hunter 422 is just 232 over a differential pair
01:05 rue_shop2 yea, that
01:06 rue_shop2 well gee, this is my first RF project that ever worked
01:07 XSerpentX cool
01:07 XSerpentX ya there is like token transactions
01:07 XSerpentX and stuff with usb
01:07 XSerpentX fun..
01:08 rue_shop2 its not high bandwidth, I can push the reciever to about 2Khz
01:08 XSerpentX decent
01:08 rue_shop2 if I used FSK I wouldn't get much data bandwidth from it
01:08 XSerpentX device ids...serial# ids
01:09 XSerpentX i increased the resolution of my pan/tilt kit
01:09 XSerpentX before i was doing a 1-9
01:09 XSerpentX so 4 ticks on each side
01:10 XSerpentX and it was really jerky
01:10 XSerpentX now i do 50 on each side
01:10 XSerpentX alot better
01:13 Shape_Shifter http://www.youtube.com/watch?v=rSKNZP33a0Y&feature=plcp&context=C3e3bb4aUDOEgsToPDskLW7GjSVYwdp_RVYP_lGmd_
01:14 rue_mohr I cant believe I got 15V out of that transmitter amp
01:17 rue_mohr ah, here they turn the bias on and off to the transmitt amp to modulate it
01:17 XSerpentX i can't believe how complicated usb is
01:17 rue_mohr amazing eh?
01:17 XSerpentX ya
01:17 rue_mohr will I crash a plane if I transmitt at 20Mhz?
01:18 XSerpentX probably
01:18 e_mohr rubs han
01:18 XSerpentX at least some ultralights
01:18 Triffid_Hunter XSerpentX: now here's the brain-bender: is it more or less complicated than necessary to provide a stable and consistent platform for all the devices it was intended to be used for?
01:18 rue_mohr yea 33Mhz is in the restraunt headset bands
01:19 rue_mohr 20Mhz is between the 15m and 17m amateur radio bands
01:19 XSerpentX less?
01:21 rue_mohr oh my digikey dosn't seem to stock cb crystals
01:21 XSerpentX i think i'm tired
01:21 XSerpentX i want a cb radio
01:21 XSerpentX i'd be so badass in the car
01:24 rue_mohr AHA! 49.86Mhz
01:24 rue_mohr they have that
01:26 rue_mohr http://www.crystek.com/microwave/admin/webapps/welcome/files/vco/CVCO55CL-0045-0070.pdf
01:26 rue_mohr $20 VCO
01:26 rue_mohr :/
01:27 rue_mohr hmm a new freq gen would be nice... my current one is tube 100khz - 110Mhz
01:35 rue_mohr so I should be able to pull a varicap out of any vcr tuner...
01:35 rue_mohr wonder if I can identify it
01:38 rue_mohr hmm
01:38 rue_mohr look for the RFC, go from there..
01:39 rue_mohr http://4.bp.blogspot.com/_5U-xK5EevrI/Rgeauev93SI/AAAAAAAAABI/EoMVxbxBZY8/s1600/Good+Colpitts+VCO.jpg
01:39 rue_mohr oops
01:39 rue_mohr 1pf??? is that a joke?
01:53 XSerpentX a small jumper wire could probably be equivalent
02:10 rue_shop2 its not a freq filter in this schematic, its a REALLY high gain amp
02:11 rue_shop2 its taking a signal that on 5V can barely be seen on my scope and easily triggering on it
02:11 rue_shop2 wow
02:38 eBear 's mind * <--- *
02:38 theBear ^^^^^ you just blew it !
03:10 rue_shop2 hahah
03:10 rue_shop2 so
03:10 rue_shop2 I put 5V on the tuning voltage of a vcr tuner to find the varicap
03:11 rue_shop2 and prettymuch every diode in the whole thing has the 5V on it
03:13 rue_shop2 I wonder if they use a local oscillator
03:13 rue_shop2 if so, you should be able to take a vcr tuner and turn it into a 49Mhz - 855Mhz freq gen
03:23 rue_shop2 aha
03:23 rue_shop2 there may be 4 varicaps, antenna filter, 2 in bandpass filter, and one in oscillator
03:24 rue_shop2 ok I think I know which ones they are
03:27 rue_shop2 hehe tobbors cycling is working perfectly
03:28 rue_shop2 did anyone notice he restarts every 2 hrs?
03:28 Triffid_Hunter hasn't renamed when his nick became available
03:30 rue_mohr ok so, WHY was I looking for a varicap?
03:30 rue_mohr oh right, I want to replace my tube freq gen
03:30 rue_mohr which goes from 150khz to 37Mhz
03:31 rue_mohr and everything else above that they do via harmonics
03:31 rue_mohr todays objective was to drill a hole in the cnc machine
03:31 rue_mohr it didn't get done...
03:42 rue_mohr WHAT!? after all that NOW I find out I can use a 1N4004!
03:58 rue_mohr now I just need to get around the JFET and I'm clear
13:46 rue_mohr I'm gonna go do nothing in my shop, its generally more productive
13:47 Steffanx No need to be in your shop on sunday anyway.. ?
14:50 jadew do you guys use some kind of software to organize your components?
15:03 Tom_itx spreadsheet
15:03 Tom_itx i wanted to write an ap but never have
15:03 jadew that was my first tought too, but an app would be nicer
15:04 Tom_itx to handle all my BOM's and reduce the inventory when used
15:04 Tom_itx etc
15:04 jadew BOM?
15:04 Tom_itx bill of material
15:04 jadew oh
15:04 jadew I think I'm gonna write one after I have my power source done
15:05 Tom_itx and keep track of the cheapest source for them
15:05 jadew yeah, that too
15:05 Tom_itx or alternate parts
15:05 jadew I figured it could search for parts on the big online shops
15:06 jadew and fetch links to pdf files, prices, etc
15:07 jadew could be js scriptable, so you could add custom sources
15:26 jadew what are darlington pairs used for?
15:27 Tom_itx power amps etc
15:27 jadew they look a lot like constant current sources
15:32 SolarNRG Hi everyone
15:32 SolarNRG I'm making a mold of a gear using clay and a steel gear with a bolt into iit, check it out: http://i.imgur.com/r8K6X.jpg
16:32 rue_mohr well I preped the rest of the battery packs for buddy, and finished one
16:32 rue_mohr but now I have to go buy parts for the truck, groceries, change the kitty litter, replace the water in the fishtank, fix a buddys computer, make supper and go to bed
16:33 rue_mohr I want to finish the battery packs and do more work on the new cnc machine that I had the chance to drill a new hole in
16:34 rue_mohr I also want to write a try out avr code for a digital oscilloscope
16:34 rue_mohr I need to ditch this sleeping thing
16:35 rue_mohr he's gonna have a hell of a time getting that gear out
16:41 Tom_itx don't kill the fish
16:41 Tom_itx yep, i'd use urethane to mold it i think
16:57 Steffanx "I figured it could search for parts on the big online shops" jadew … octoparts.com ?
16:57 jadew farnell.com
16:58 jadew has a really nice filter
16:58 Steffanx No, that's not a 'search for parts on the big online shops' website :)
17:00 jadew why not?
17:01 Steffanx Farnell is such a website?
17:02 jadew yeah, the filters they have allow you to pinpoint components with the exact specs you need
17:03 Steffanx True, but it's farnell only, and octoparts.com is .. not farnell only
17:03 jadew yeah, but I don't really care what other sites have, farnell is in delivery range for me, no VAT
17:04 jadew well, no additional taxes
17:04 jadew vamal and stuff
17:04 jadew cuz the VAT will be there
17:04 Steffanx Hmm, don't say "search for parts on the bigs online webshops" then next time :P
17:04 Steffanx *big
17:05 jadew ok :)
18:52 jadew hey, in this schematic: http://baec.tripod.com/MARCH92/pics/adjustable_power_supply.bmp
18:53 jadew wouldn't the load affect R14, therefore changing the gain?
18:53 jadew since the gain will be R14 / R12
18:54 jadew so if load is in paralel with R14, it will lower it, therefore lowering the gain as well
19:04 jadew well, R14 + R12 / R14
19:04 jadew anyway, the load should generate a change in R14
19:22 rue_mohr uh ho linear power supply
19:23 rue_mohr R14 and R15 are a voltage divider thats used for feedback to the comparitor with the reference voltage
19:23 rue_mohr current is sensed with R10
19:23 rue_mohr 0R15 means 0.15 ohms
19:24 rue_mohr as 2v7 is not a typo, its 2.7V
19:24 rue_mohr jadew,
19:24 jadew I'm reading
19:24 jadew :)
19:26 jadew let me make a screenshot of what I have
19:26 rue_mohr IC1 forms a reference voltage and IC2 is an error amplifer
19:27 jadew I find it hard to understand other people's schematics, cuz I don't know how everything works
19:27 rue_mohr it limits the current by changing the reference
19:27 rue_mohr they have a lot of junk mixed in there
19:28 rue_mohr TR1 is a 30V regulator
19:28 jadew ok, here's what I have: http://imagebin.org/198625
19:29 jadew let me tell you first what I tried to do
19:29 jadew and you can tell me how I did it wrong
19:29 jadew so I got that opamp and I want to feed it some voltage while getting another on the other side
19:30 jadew I wanted to amplify the current and used that darlington chip
19:30 jadew everything works fine, except that the voltage varies with the resistence of the load
19:31 jadew I figured it's either because: a) the resistence of the load changes the voltage divider's resistence
19:31 jadew or because the resistence of the load affects the B-E current (which is probably true)
19:32 jadew however, I couldn't get it working with a pnp darlington
19:34 jadew any suggestions?
19:35 jadew oh snap
19:35 jadew got it working
19:35 jadew connected R1 to the emiter of the darlington
19:35 jadew that provides an accurate voltage of the output
20:35 Tom_itx rue_mohr
20:35 Tom_itx what did we do in class saturday?
20:45 jadew ok, I think I learned something today
20:47 Tom_itx your goal should be to do that every day
20:47 jadew kinda is
20:48 jadew a power source is indeed a good beginer's project
20:49 jadew I don't know why it didn't go all the way down to 0 in my simulation tho, it stopped at 4 millivolts
21:11 Triffid_Hunter jadew: yeah of course the voltage will vary with load
21:11 Triffid_Hunter jadew: take the feedback from after the transistor
21:11 jadew Triffid_Hunter, that's what I did
21:11 Triffid_Hunter jadew: ie move R1 to Q1's emitter rather than its base
21:11 jadew yep
21:11 jadew it worked like that
21:12 jadew however I still get a small current on the output of the opamp when I have 0 volts on V+
21:12 Triffid_Hunter jadew: and then you'll be held hostage by the open loop gain of the op-amp. LM358 is fine for mucking around but you need PID if you want the output voltage to stay exactly on some set point
21:12 Triffid_Hunter jadew: yeah most op-amps can't drive their outputs to either power rail, you need a special rail-to-rail op-amp for that
21:13 jadew ah, I see
21:13 jadew what is PID?
21:13 Tom_itx feedback loop control... Proportional Integral Derivative
21:14 Triffid_Hunter jadew: it's a loop control method that not only looks at how far away the output is from the set point, but also how long it's been different and how fast it's moving
21:14 Triffid_Hunter jadew: at the moment, you have proportional control- the output current is proportional to the difference between output voltage and setpoint voltage multiplied by some gain value
21:15 Triffid_Hunter jadew: so your output will always sag by some amount with load current
21:15 jadew I see
21:15 Triffid_Hunter jadew: to compensate for that, you need to detect that it's been sitting too low for some time, and boost the output a bit. this can be done with an integrator
21:16 Triffid_Hunter jadew: ps: chuck 'op-amp integrator
21:16 Triffid_Hunter ' at google images for a plethora of examples
21:17 jadew can't tell what's going on from the images, will have to read on it
21:17 Triffid_Hunter jadew: but now you have the problem that if you change the set-point or load suddenly, the integrator winds up and your output will over-shoot the setpoint and may even oscillate. Alternatively, it may be slow to respond. So we need to detect how fast the output is approaching the set-point, and shut down the drive a bit earlier. we can use a differentiator for this
21:18 Triffid_Hunter jadew: do you know what happens to a capacitor when you feed a constant current into it?
21:18 jadew yeah
21:18 jadew it charges and stops additional current from flowing once it's charged
21:18 Triffid_Hunter jadew: but what does the voltage on the capacitor do?
21:19 Triffid_Hunter jadew: http://www.allaboutcircuits.com/vol_3/chpt_8/11.html
21:19 jadew thanks
21:22 jadew I'm so sad a new work week starts
21:23 jadew I'll have to test the integartor thingie when I'll receive my order
21:23 jadew I need to see what's going on on an oscilloscop
21:23 jadew *oscilloscope
21:23 Triffid_Hunter jadew: get some NE5532s, they're excellent op-amps for experimenting
21:23 jadew already ordered some
21:23 jadew not of those
21:23 jadew but some op amps
21:23 jadew including a rail to rail one
21:23 Triffid_Hunter jadew: fwiw, I've done all my learning without a 'scope. they sure are handy but you can make do without
21:23 Triffid_Hunter jadew: ah cool
21:24 Triffid_Hunter jadew: there's so many different op-amps, it takes quite a while to understand what's important about each one and which situations it's appropriate for
21:24 jadew they make the process faster and that's good
21:24 jadew cuz I don't have a lot of time
21:25 jadew btw, zener diodes are meant to be used with current going the opposite way, right? so you would get a constant voltage drop across them
21:26 Triffid_Hunter jadew: yes they're used in reverse breakdown
21:26 jadew thanks
21:26 Triffid_Hunter jadew: if you forward bias them they act exactly like a normal diode
21:27 Triffid_Hunter jadew: ps: their reverse breakdown voltage is specified at some nominal current, it does change with current so don't expect a 5v zener to give you 5v at both 0.1mA and 100mA
21:27 jadew I see
21:27 jadew that's good to know
21:28 Triffid_Hunter jadew: I've had a few neat ideas for making a nice reference from them though.. basically have a weak pull-up to Vcc then an op-amp doubling the voltage and feeding that through a resistor back to the zener so it acts as a reference for its own constant current supply
21:28 Triffid_Hunter then you'll only see the variation from temperature
21:28 Triffid_Hunter can use diodes as thermometers. their forward drop changes by almost exactly 2mV per degree celsius over a usable temperature range :)
21:29 Triffid_Hunter not sure how zener reverse breakdown changes with temperature, but I'm certain that it does
21:29 jadew heh that's interresting
21:30 Triffid_Hunter jadew: see http://sound.westhost.com/project42.htm for one example
21:30 Triffid_Hunter jadew: exploits the fact that forward voltage /drops/ with increasing temperature, so a string of diodes in parallel will read as the hottest diode
21:31 jadew that's pretty cool
21:31 Triffid_Hunter jadew: personally I'd use a power mosfet to switch the fan rather than a darlington BJT
21:32 Triffid_Hunter apart from that it's a neat demonstration
21:32 Triffid_Hunter jadew: here's a test for your electronics eye: what is R4 for?
21:33 jadew hmm
21:33 jadew hold on
21:33 jadew looks like neg. feedback
21:34 jadew but I'm not sure
21:34 jadew give me a bit more time
21:35 jadew yeah, that's what it has to be
21:36 Triffid_Hunter jadew: sure, so what effect does it have? and what effect would it have if it were connected to the op-amp's + input?
21:37 jadew ok, let me see if I can understand how the circuit works
21:38 jadew R1 looks like a pullup resistor
21:38 jadew voltage drop on the diodes, trough R2 to ground
21:39 jadew I don't know what's the purpose of R3
21:40 Triffid_Hunter R3 could probably be shorted and it would still work
21:41 jadew yeah, I don't know why it's there, I don't fully understand the circuit
21:41 jadew V+ will always be bigger than V-
21:42 jadew so the opamp will push some voltage on it's output
21:42 Triffid_Hunter then the fan will never turn on ;)
21:43 jadew well, it will push until V- = V+
21:43 jadew but I still don't know what's the purpose of R4, altho that's where the current goes trough
21:46 jadew yeah, can't get it, I think I'll need to read a bit more on opamps, the reason I can't get it is because I don't know what the opamp will do in specific situations
21:47 jadew oh well, thanks for the info, I have to go to bed, it's 5am
21:52 Triffid_Hunter jadew: ok, chat later :)
21:52 jadew yes, thanks again
21:52 jadew night
23:10 rue_mohr Tom_itx, the new kid did his first soldering, and worked on some code to controll a stepper motors, but I'd miswired the driver and didn't find the error in time,
23:10 rue_mohr the kid that does stuff worked on the code for the arm that saves and recalls positions of motors
23:10 rue_mohr and the kid that hasn't done anything in forever played minecraft more
23:16 rue_mohr oh I finished making the last of the battery packs for buddy
23:16 rue_mohr I'm just going thru charging them all up
23:25 rue_mohr I have a flow chart infront of me thats REALLY simple and I dont have time to code it
23:45 XSerpentX nice
23:45 XSerpentX i am stabilizeing my circuitry
23:45 XSerpentX and working on power supply
23:45 XSerpentX is it ok rue, if i build a power supply say
23:46 XSerpentX 8x AA batteries
23:46 XSerpentX in series
23:46 XSerpentX can you take voltages from them where u need it?
23:46 XSerpentX like say i took from 6v and then from 9v and then from 12v
23:47 XSerpentX had like 3 wires coming from it
23:47 XSerpentX that all return to the same ground
23:47 rue_mohr yes, but some cells will die faster than others
23:48 XSerpentX my other ideas is to regulate the 12v
23:48 XSerpentX to 5v
23:48 XSerpentX 2 components will use the 12v
23:48 rue_mohr if its not a switching regulator, tap the batteries
23:48 XSerpentX and the rest the regularted 5v
23:48 orlok hmm
23:49 orlok i turned a big multi function printer into parts the other day
23:49 orlok only one stepper!
23:49 orlok but lots of DC motors with encoders
23:49 XSerpentX neat
23:49 rue_mohr you got rid of the roms?
23:49 rue_mohr orlok, good! use them!
23:49 rue_mohr steppers suck
23:49 orlok and then i went and worked on my software
23:50 XSerpentX why u think steppers suck rue
23:50 orlok i have delay based actions happening
23:50 rue_mohr casue they are slow
23:50 XSerpentX ah
23:51 rue_mohr and their torque drops off the faster they go
23:51 rue_mohr I'll agree they are really convienient
23:51 rue_mohr esp 5 and 6 wire ones
23:51 rue_mohr aka unipolar
23:51 rue_mohr oh wow, I just had a thought
23:52 rue_mohr how cool it would be to be at a convention of people like you and me
23:52 rue_mohr to have more than 4 people in a room who know what a stepper is
23:52 e_mohr awe's at the tho
23:52 XSerpentX we have something like that in my sist
23:52 XSerpentX city
23:52 XSerpentX they call them makerspaces
23:52 XSerpentX they have linux parties and stuff
23:53 XSerpentX and community projects
23:53 XSerpentX like those 3d printers
23:53 rue_mohr yea, I'm the closest person to having a makerspace there is
23:53 XSerpentX ya..bc
23:53 XSerpentX not to many geeks there..
23:55 XSerpentX so any tips about making battery packs?
23:55 Triffid_Hunter rue_mohr: the torque only drops off with speed if you drive them with constant voltage
23:56 Triffid_Hunter rue_mohr: constant current drive keeps the torque relatively constant, certainly more stable than a DC motor!
23:56 rue_mohr even const current will only go so fast
23:56 rue_mohr feedback
23:56 rue_mohr feedback makes it all good
23:56 XSerpentX i was thinking of just taping them up with electrical tape
23:57 Triffid_Hunter rue_mohr: sure, but if you want fast use a 3-phase synchronous motor like the "BLDC"s
23:57 Triffid_Hunter rue_mohr: which I consider to be essentially a 3-phase stepper
23:57 rue_mohr well yes
23:57 rue_mohr I'm not there yet
23:57 XSerpentX and making little contacts and taping them
23:57 rue_mohr I have some 5 phase bipolar steppers
23:57 XSerpentX or u think i should just get 2x4 battery holders
23:57 rue_mohr 10 wires!
23:57 Triffid_Hunter XSerpentX: gladwrap works well for battery packs, it shrink-wraps when they warm up from charging :)
23:57 rue_mohr I'm gonna play with those one day
23:58 XSerpentX cool
23:58 XSerpentX i think for my first pack, i'm genna use alkaline
23:58 XSerpentX just cuz my first one will probably be shitty
23:58 rue_mohr a cell phone battery is about 1Ah and charges to 4.2V
23:59 XSerpentX yeah
23:59 XSerpentX is that a good idea
23:59 XSerpentX to use two different batteries?
23:59 rue_mohr no
23:59 XSerpentX like i was thinking that
23:59 rue_mohr you have to charge cell phone batteries really carefull yoo
23:59 XSerpentX a 9v regulated for the electronics
23:59 rue_mohr too
23:59 XSerpentX and a 12v for the dc motor