#garfield Logs

Feb 01 2014

00:00 katsmeow-afk no wonder they move so fast
00:02 rue_house I have a no load somewhere
01:57 rue_shop2 to protect a 20mA meter, looks like I can use the BE junction of two PN2222 transistors back to back...
01:59 rue_shop2 the datasheet implies it can take 50mA
02:01 rue_shop2 I need something that can take more current
02:01 rue_shop2 root@freebee5:/files/programming/src/pronterface/Printrun# ohm -v 25 -i .05
02:01 rue_shop2 Wattage is: 1.250000
02:01 rue_shop2 Current is: 0.050000
02:01 rue_shop2 Voltage is: 25.000000
02:01 rue_shop2 Resistance is : 500.000000
02:01 rue_shop2 root@freebee5:/files/programming/src/pronterface/Printrun# ohm -r 500 -i .02
02:01 rue_shop2 Wattage is: 0.200000
02:02 rue_shop2 Current is: 0.020000
02:02 rue_shop2 Voltage is: 10.000000
02:02 rue_shop2 Resistance is : 500.000000
02:02 rue_shop2 according to that, if I put the protection diodes in, and use a series 500R resistor, then at 20mA I have 10V drop which is too much
10:42 katsmeow-afk you could use the BE of a couple of 2222 transistors, but why not use a couple of 1N4148/etc diodes? they are smaller, faster, lower capacitance, cheaper, have a higher reverse voltage rating, and can carry more current
10:52 rue_house I did some curve tracing, the shottkey diodes (0.2V) better than PN2222 BE (0.8V)
10:53 rue_house at 20mA the meter only has about 60mv across it
13:59 katsmeow-afk you can cancel half the drop if you use a 3rd diode tween them, biased on already, get it down to .1v, use an opamp to get it down even lower
14:03 katsmeow-afk you going to get those 74F269's? http://www.ebay.com/itm/360848755840
14:04 katsmeow-afk i don't wanna pay that much for s&h, it's just not worth it if i cannot combine it with something else he has, which atm he doesn't
14:10 katsmeow-afk he's now doing shirt like http://www.ebay.com/itm/8-PCS-CYPRESS-SEMICONDUCTOR-CY7C1399-12ZC-/390760698637 , where if you win it for the min bid of $3, you are still paying $2.50 per chip unless you combine s&h with something else
14:19 katsmeow-afk http://designerthinking.com/images/MeterProtection.JPG <<== vary the clamp voltage by changing type of diodes and/or varying the current (voltage drop) thru the R-D-R path on the left
14:21 katsmeow-afk if you use a peak-reading type of opamp circuit that lite "CLIPPING" leds on audio equipment, you canvaryt he R-D-R current dynamically, and it's prolly fast enough to keep the meter quite safe
14:23 katsmeow-afk with opamps, you canreplace the R-D-R with R-R-R and a C across the middle R, and tune it to mere millivolt accuracy clamp range
14:23 katsmeow-afk be sure to float it all to whatever the meter voltage is reading on
14:25 katsmeow-afk should be easy to do with a t13, using the pwm thru RC pi circuit to tune the analog voltage thru the R-D-R or R-R-R path
14:25 katsmeow-afk or anything else
14:25 katsmeow-afk prolly 100 ways to do it
14:25 katsmeow-afk but anyhoo, that's basically how you can offset and cancel the diode drops
14:27 katsmeow-afk use 2 diodes if you like, R-D-D-R
14:27 katsmeow-afk use 3 diodes if you like, R-D-D-D-R
14:27 katsmeow-afk all depends on what you wanna clamp, and/or pass, and in which polarities
14:29 katsmeow-afk i often found it handy to make a D-R-D in a 5v ttl system, to generate 0.7v and 4.3v , so i could diode clamp pretty exactly at 0v and 5v
14:31 katsmeow-afk works for protecting opamp inputs when the signal is coming from an unknown place too,,, in the olden daze some opamps would latch like flipflops if the input voltage went over Vcc or under Vee
14:33 katsmeow-afk pick the Vdrop from schottky, germanium (1N914, etc), or vanilla diodes, or back-to-back zeners (yuck)
14:34 rue_house ah
14:35 rue_house the trick being that its a 20mA ammeter...
14:35 rue_house hmm
14:35 katsmeow-afk with a 20ma meter, people usually buffer them and drive the meter with an opamp circuit that cannot drive more than 20ma anyhow
14:36 rue_house I'm thinking two shottkey diodes and a 60ma fuse
14:37 katsmeow-afk really? the opamp would prolly be cheaper and smaller
14:37 rue_house if someone is gonna make a mistake, its prolly gonna be a big one and the meter would only get the 200mV for an instant
14:38 rue_house its for a processd control meter
14:38 katsmeow-afk set the opamp for a gain of 1, let the circuit you measure feed a resistor, use a 500k resistor to each opamp input, opamp drives meter, TL081/61/71 can deliver only 20ma anyhow, it's al self-protecting
14:39 rue_house I have a buckboost power supply, can do 1.2 to (24)V out, the 20mA meter, and I built a 2-22mA dummy sender (with pot)
14:40 rue_house 6 terminals, (power, meter, sender)
14:40 katsmeow-afk well, anyhoo, that's how i'd do it
14:40 rue_house yup, I have some 5V->9V isolated power modules for thicknet
14:40 katsmeow-afk the 500k R would protect the opamp, the opamp protects the meter, no fuse to replace, and its' 1000x faster than a fuse
14:41 rue_house the inertion resistance shouldnt be more than 20 ohms or so, or the loop voltage drop starts to add up
14:41 tsmeow-afk shrugs and goes back outside to jackhammer dirt and shovel dirt and move dirt, since she can't design electro
14:42 rue_house get me pics!
14:42 katsmeow-afk the 500k is outside the "loop"
14:42 e_house
14:42 rue_house hmm
14:42 rue_house I shall play with this idea
14:55 rue_house 32k static ram chip
14:55 rue_house but, I have 386/486/586 processor cache chips that are static ram, that are larger than that
15:21 rue_house or are they in bits
15:22 rue_house the 512k ones would still be 64k
15:22 rue_house at 8 bits
15:45 tsmeow-afk has collected cache and main memory modules when bottom feeding, because even a 128megabyte module is 16megabyte x 8bit chips, you can cram a lot of log data from an avr on
16:49 katsmeow-afk it may be 60f outside, but i am sweating like ... umm, something that sweats a lot when overworked
16:50 m_itx doesn't seem to think it's 60F out
16:51 katsmeow-afk he doesn't?
16:52 katsmeow-afk web sais it's 63f here atm, which is a lil highfor Feb 1
16:52 Tom_itx 28� F
16:52 katsmeow-afk yipes
16:52 katsmeow-afk no wonder storms are forecast for tonite
16:54 katsmeow-afk oh, they are calling the storms "fog" now, storms have been postponed till tomorrow evening
17:02 katsmeow-afk which is great, because the cement i poured yesterday it's really set up well yet, and i hae fresh fiberglas resin poured
17:02 katsmeow-afk bbl
17:57 katsmeow-afk ......
18:01 katsmeow-afk http://www.ebay.com/itm/-Briggs-Stratton-185HP-OHV-31P777-Intek-Engine-Starter-/191057582589
18:02 katsmeow-afk http://www.ebay.com/itm/Briggs-and-Stratton-17-hp-starter-/151223044526
18:04 katsmeow-afk http://www.ebay.com/itm/SNAPPER-COMET-LAWN-MOWER-BRIGGS-STRATTON-STARTER-11-HP-1-/141181098022
18:04 katsmeow-afk http://www.ebay.com/itm/SNAPPER-COMET-LAWN-MOWER-BRIGGS-STRATTON-STARTER-11-HP-2-/131107146621
18:05 katsmeow-afk the last two are baby ones, but $20 free s&h
18:05 tsmeow-afk is not bid
18:06 tsmeow-afk hopes someone running across small cheap servos will clue her in on
18:06 katsmeow-afk 5,791 results for measuring spoons
18:08 katsmeow-afk sheeeeeeeeze, people are pricing these like $2 per spoon
18:22 katsmeow-afk news just said some places ran out of sand and had to BORROW sand ,,,,,,,,,, i would sure like to see them collect up that sand and return it to whoever they borrowed it from
18:24 Tom_itx the wind and rain will help them
18:25 katsmeow-afk help them collect the sand so they can return it?
18:32 katsmeow-afk today "the tempachers were wooooorm" <shudder>
18:48 katsmeow-afk if people no longer fight in wars, but instead fight wors, then why send still armies instead of ormies?
19:23 rue_shop2 ok I doubled the light output of the converted knock fixture
19:24 rue_shop2 they should collect the sand from the drains it ended upin
19:25 rue_shop2 dosn't ship to canada
19:38 rue_shop2 ok, if my understanding is right, I can change the temp sensor pullup resistor on the reprap and trick it into stepping some motros for me
21:40 Tom_itx damn good nap
21:40 Tom_itx dunno if i feel worse or better though
22:01 katsmeow-afk you will need to find someone localto you to feel you and verify , we cannotdothat from our locations
22:06 rue_shop2 wait, i can make a robot
22:06 rue_shop2 I can make it prod really hard...
22:19 katsmeow-afk seller tries to tell me the item was shipped and delivered to me FedEx, despite http://news.van.fedex.com/usps-and-fedex-renew-global-express-guaranteed-agreement
22:20 katsmeow-afk i also have pics of the package, it has NO FedEx name on it anywhere, but it DOES have USPS on it
22:20 katsmeow-afk i'd give you the url, but rue logs, zlog logs, and google will give everyone logged my addy
22:24 katsmeow-afk woah @ https://dl.dropboxusercontent.com/u/183289187/honeycomb/why-yacht.jpg
22:36 rue_shop2 dear god, someone has a cnc machine and WAY too much time
22:36 rue_shop2 that has to be the MOST elaborate wood structure I'v ever seen
22:37 rue_shop2 and the cleanest floor
22:37 Tom_itx that looks like a RUE size project
22:37 katsmeow-afk i wonder what will become of it
22:37 Tom_itx termites
22:37 katsmeow-afk i wonder if it floats with all those lil square holes in it
22:37 rue_shop2 that looks like steel plates
22:38 katsmeow-afk gonna take a ton of caulking
22:38 rue_shop2 or a few
22:38 Tom_itx hope no tree huggers see that
22:38 katsmeow-afk i wonder if there's space inside for anyone taller than 4 or 5 inches
22:39 e_shop2 thinks of that method for building his
22:39 katsmeow-afk i know, stuff inflated party balloons in the holes,, maybe if helium is used it will fly
22:44 rue_shop2 oooo a true air-ship
22:45 rue_shop2 much more desirable than an error-ship
22:46 tsmeow-afk
22:52 rue_shop2 FFFFFFFFF aparently NOBODY (commercial manufacture) builds things with #20 grey wire }:|
22:54 katsmeow-afk pata ribbon cable?
22:57 Tom_itx i got 2 spools of 28ga
22:57 Tom_itx ribbon
22:58 katsmeow-afk i dunno how much i have of it
22:59 katsmeow-afk surely everyong has some, after all the cable don't break, the conenctions inside the crimp connects break
23:00 katsmeow-afk i bet your neighbor's car has some grey wire in it
23:03 katsmeow-afk this is why , when at the recycler, if i see 4ft of cable, i peel it back a lil to see if it has anything in it i need, like grey #20 wire
23:04 katsmeow-afk btw, you need 50ft of 20 pair shielded audio snake?
23:05 katsmeow-afk hmm, i wonder if it's good at video speeds
23:08 katsmeow-afk rue : http://www.motherjones.com/blue-marble/2014/01/keystone-xl-its-just-obama-now <<== becha Obama approves it now
23:09 rue_shop2 its funny, where i used to have a problem and think of a solution I needed a lathe to implement, now, I go further and think of a solution that dosn't need the lathe
23:09 Tom_itx silly rue
23:10 Tom_itx does it need a new tool you don't yet have?
23:10 katsmeow-afk that simply means the lathe doesn't have enough attachments
23:10 tsmeow-afk high-5's
23:10 rue_shop2 kat, we just had our revolts against the pipeline going thru here
23:10 katsmeow-afk i know, now it's time for the usa to be revolting
23:10 katsmeow-afk err, that doesn't sound right
23:11 rue_shop2 tom, no, now that I have a lathe, I think past the solutions that need it, and usually find out that there is a way to do the solution without the lathe
23:11 rue_shop2 hahah :)
23:11 rue_shop2 I heard what you meant first :)
23:12 katsmeow-afk ;-)
23:12 rue_shop2 this led-converted fixture I did puts out quite a bit of light with double the leds
23:12 rue_shop2 but.. its kinda warm
23:13 rue_shop2 even tho its only .5A I dont think that laptop supply is being that efficient
23:14 katsmeow-afk it isn't , i calc 80%
23:14 katsmeow-afk they 1) do not plan on it being on long enough to get hot, 2) don't put a fan on it (which you prolly need)
23:15 rue_shop2 its rated for like 3.5A, I'm running it at about .5
23:15 rue_shop2 then again, i have it boxed up in a metal container
23:15 katsmeow-afk same as my lil 500w UPS, the heatsinks were blocks of aluminum, no fins, no fan, the battery dies before the alum gets hot, and they cool off before the battery canbe recharged
23:15 katsmeow-afk 3.5 PEAK
23:16 katsmeow-afk that is why this line was so important : [19:07] <katsmeow-afk> cut fence too,, if the house stays warm i may go back up to wirebrush some steel, and i discovered way to not saw laptop psu on the bandsaw
23:19 rue_shop2 you shoudln't use a laptop supply to run a bandsaw, it'll stall out and fail, taking up more time than if you were running it off 120 direct
23:19 rue_shop2 ;)
23:19 rue_shop2 ok I'm getting dizzy, where is some supper...
23:19 katsmeow-afk true
23:20 katsmeow-afk but it was difficult to find ways to not saw up laptop psus
23:27 katsmeow-afk rue, what happened to putting the leds in series right on the 120vac line?
23:29 tsmeow-afk doesn't know the Vdrop of rue's diodes, or she'd be calculating stuff
23:29 rue_shop2 the line voltage is all over the map here
23:29 katsmeow-afk so? one-trasistor current source will handle that
23:29 rue_shop2 I wouldn't want the leds damaged when there is a spike
23:29 rue_shop2 also, kinda nice not to worry about isolating the leds
23:30 rue_shop2 they are lick-safe
23:30 katsmeow-afk well, that depends on the psu, some have a few megohms, and a capacitor, to one of the two 120vac power wires
23:30 katsmeow-afk some don't
23:35 katsmeow-afk http://www.trainweb.org/girr/tips/tips7/lm317_led_regulator_ckt.gif
23:37 rue_shop2 kat, I was thinking about colour-coding nuts/bolts/screws on robots so that, as they fall off, you can know what they were from, it just occurred to me that structural and nonstructural might be two good starting catagories
23:37 rue_shop2 ]:}
23:38 katsmeow-afk well, yeas
23:38 rue_shop2 cause, why solve a problem when you can go to effort to understand it better
23:38 rue_shop2 :)
23:39 katsmeow-afk i was driving down a country road one day, saw what i wanted to see, turned around and was driving back home and noticed a bolt that looked a LOT like one of my car's engine mount bolts in the middle of the road
23:39 katsmeow-afk turns out, it WAS one of my engine mount bolts
23:40 rue_shop2 good eye
23:40 katsmeow-afk but my point was: no paint
23:40 rue_shop2 did I tell you while I was last under my truck fixing the exhaust pipes, I notied that both bolts that hold on the back of the transmision were missing?
23:41 rue_shop2 I did a trippletake
23:41 katsmeow-afk no, you didn't tell me that, are you ging to tell me?
23:41 rue_shop2 I'll save it as a story for later then its got good context
23:41 katsmeow-afk ok
23:42 katsmeow-afk did you paint the new bolts any particular color?
23:43 katsmeow-afk some bolts i now goop up with an adhesive or a sealer or something, and i believe a lot in nylocks unless they get hot and melt the nylon
23:43 katsmeow-afk other bolts i use a coppery anti-stick on
23:44 katsmeow-afk for instance, the grade-8 bolt holding the trailer hitch on has a nylock
23:45 katsmeow-afk any time i take a brake rotor off, i paint the hub's mating surface with copper anti-sieze
23:46 katsmeow-afk had to cut one off the car once, then grind the surface flat again
23:49 katsmeow-afk sorta like this problem, when the bearings had siezed inside the ,, whatever that thing is called : http://designerthinking.com/images/carhub/yep,%20it%27s%20bent.jpg and i reground it to be http://designerthinking.com/images/carhub/now,%20less%20bent.jpg
23:49 katsmeow-afk because, http://designerthinking.com/images/carhub/i%20resurfaced%20it%20in%20place.jpg
23:50 katsmeow-afk wasn't perfect, but it works
23:52 rue_shop2 oo
23:52 rue_shop2 damn your good with a grinder
23:52 katsmeow-afk i made a current source with one transistor for a 600vac feed to a flourescent once, the goal was to not use ballasts, and to force the lamp on instantly
23:53 katsmeow-afk <curtsey>
23:53 rue_shop2 I want you to design a jig to grind back the jaws of the new vise flat so the inserts have a flat resting surface and dont crack/break away when material is tightened in it
23:53 rue_shop2 I been trying to think how you might do it, but its not comming to me
23:54 rue_shop2 I might resort to asking you
23:54 tsmeow-afk looks forward to you asking
23:54 rue_shop2 but one of the guys I know has a milling machine, so I dont know what will happen first
23:54 katsmeow-afk can you get the vise off the table and flip it onit's back, and secure it ?
23:55 rue_shop2 its back!? ...
23:55 rue_shop2 top down?
23:55 katsmeow-afk upside down!
23:55 e_shop2 didn't think about anything like
23:55 rue_shop2 I suppose it could be mounted via the anvil
23:56 Tom_itx kurt vise
23:56 rue_shop2 hu?
23:57 Tom_itx cadillac of machine vises
23:57 katsmeow-afk vise grip the two faces tight together, set the vise on them,, or set them up in the vise, where they supposed to go, then shim from the bottom, when you cannot insert more shims, pour in 2-part epoxy, let harden, then flip right side up, remove visegrips, open vise, insert the screws
23:58 Tom_itx what's the hub off of?
23:58 katsmeow-afk by "insert screws, you could have them already inserted partially, or use alignment pins to be more precise, but don't fill the bolt holes with epoxy
23:59 katsmeow-afk the hub i ground? it's shown on the car, when is where i ground it in place, the Ford Probe, front
23:59 Tom_itx was it bent?
23:59 katsmeow-afk http://designerthinking.com/images/carhub/yep,%20it%27s%20bent.jpg