carlynorama

the blog

Options for coating craft foam & styrofoam to create a smooth finish

by Carlyn Maw on August 22, 2011, no comments

Foam can be eaten away by non-water based products. ??Acrylic-Paint-Compatible supplies will work. Paint requires A LOT of coats. Some thicker options for a faster smoother??base coat??below.??

Industrial Products

Styrospray 1000 Foam Coatings??

requires hopper gun.

Foam Coat
Hard, crust-like shell for expanded polystyrene (foam). Developed as an alternative to Vanillacryl (TM). Tough and hard. Can be cut and machined.

Slower process than Styrospray.

More Products

DIY

Replica Props Forum
  • Brushed or rolled on layers of white glue or Mod Podge (it's just white glue) will be the cheap option…
  • If you want a more 'rock' like surface, a 50/50 (give or take) blend of a latex primer and plaster joint compound rolled on will get a real hard coating…

Van's Super Scenic Dope Recipie?
?? ??
??"So Van, I went to tell a friend about your VSSD and when I did the search I found 3 different recipes. I assume that means you don't really have a recipe and sort of fake it. I thought I would post this on the boards instead of in a P.M. because your VSSD sounds like a cool product we all should mess with a little. Could you choose one for us to follow as a starting point and maybe comment on what happens if you alter the ratios. Thanks!" (answer, #3 for rocks, 1 or 2 for a thiner coat)

?? ?? Below are the recipes you have posted in the past.

?? ?? Recipe #1
?? ?? "3 qts flat latex paint < any color, good place to use up all the left over paints from the scenic painters shop>
?? ?? 3 – 5 tubes acrylic latex painters caulk ( often called Alex caulk)??
?? ?? 1 cup Joint compound

?? ?? Recipe #2
?? ?? 1 gallon latex paint
?? ?? 2 tubes Latex painters caulk. < not silicon>
?? ?? 1 cup Joint compound
?? ?? 1/2 cup water putty

?? ?? Recipe #3
?? ?? "about 1 quart of latex paint ( this can be pretinted, neutral base, or a "waste" paint, as long as it's latex.
?? ?? About 4 tubes of Latex caulk. Do not use Silicone caulk. Some Latex caulk are called 'siliconized' and those are ok to use as they are still latex based.
?? ?? About 2 cups of drywall mud. Adds thickness and aids in setup time and helps leave a harder finish when dope is cured."

From the Manufacturers

The makers of Styrofoam??? ??http://www.styrofoamcrafts.com/tips/
  • Paint with an acrylic craft paint. Solvent-based paints may damage the foam (see paint manufacturer's instructions for details). Use a brush with stiff bristles for the best coverage. Place small shapes in a zip-top plastic bag, add paint, seal the bag, and rotate shape until it's completely covered. Remove from bag with pick and let dry."
  • Use spray paint with caution; read the label carefully to determine whether or not it???s safe for STYROFOAM Brand Foam.
  • Hint: Insert a floral pick or wood skewer into your foam shape to use as a handle while painting. When done, insert the handle into a block of STYROFOAM Brand Foam while paint"
  • Cover foam shapes with plaster, wallboard compound, gesso, modeling paste or other coating materials??
  • Smooth it or stucco it, swirl it or sculpt it

Button Research

by Carlyn Maw on August 19, 2011, no comments

These are some of the buttons found for the trigger. I still vote for
the if you stick something-up-the-tube-it-goes-on trigger but this
gives us options.

I like red buttons – but red buttons can mean STOP or Emergency STOP!
In certain contexts. Don’t know if that matters. The Illuminated
buttons allow for custom art, now and in the future.

ADA Door Style:
http://www.alibaba.com/product-gs/279657574/LARGE_SIZE_EXIT_DEVICE_PUSH_BUTTO…
http://www.disabilitysystems.com/switches/

Jumbo Domes:
Illuminated: http://na.suzohapp.com/pushbuttons/954002xxxxz.htm
Not Illuminated:  http://www.arcadespareparts.com/arcade_parts/push_buttons/arcade_button_jumbo… 
More Illuminated (Green?): http://www.arcadespareparts.com/arcade_parts/push_buttons/arcade_button_dome_… 

http://www.sparkfun.com/products/9181

MISC:
Button Manufacturer (for sale on DigiKey) (largest only seems 2 in?) http://www.apem.com/pushbutton.html
Touch Pad Switch and Other Interesting Options: http://www.mcmaster.com/#touch-pad-switches/=dolfvl
Big Red Emergency Stop Button: http://www.grainger.com/Grainger/LOCKNETICS-Standard-Push-Button-1RAD8?Pid=se…

Eagle 30/30 No. 30 – Stepper Motor Driver Based on Psuedo-Breadboard

by Carlyn Maw on June 30, 2011, no comments

Made it!

So it has been a busy couple of days but I squeaked the last two in. Both with an auto-route sadly.  This one if with a fake breadboard layout that I need to clean up. THe idea is to print it on a board that looks like a breadboard to it could be copied.

One day I’ll find a board house that prints multiple colors…

Eagle 30/30 No. 29 – Stepper Motor Driver Based on Breadboard Instructable

by Carlyn Maw on June 30, 2011, no comments

Doh… so close and yet so far, it just turned midnight…

Based on a very old rough draft for an instructable that got published itself when I combined two accounts:

It needs a serious edit, I hadn’t even realized it was live, I don’t think.

This post will definitely need an update, too!

 

Eagle 30/30 No. 26 – Protected Power-only from USB

by Carlyn Maw on June 26, 2011, no comments

This circuit features a part I only learned about recently: a PTC resettable fuse.  The PTC standes for Positive Temperature Coefficient. In brief these parts are designed to melt and break the connection like any fuse if they are getting too much current. Once the current goes away, however, after some time they’ll go back to normal.  Nifty.

USB ports don’t like it when asked to source more than 100 mA. The higher power ports will acquiesce up to 500 mA, though.  This circuit has a 250 mA breaker on one line and then another in parallel that can be put into play via the BOOST jumper. That is, boosted the circuit will pass 500 mA.   LEDs are current sucks if you are pushing the limit, so those are optional via the LEDS jumper. Adding LEDS more than doubled the part count, but they are useful for trouble shooting. 

For more info: 
Selecting a PTC Resettable Fuse and TVS Zener Diode: http://forum.sparkfun.com/viewtopic.php?p=84708

 

Eagle 30/30 No. 23 – Monostable Multivibrator, 0.0.1

by Carlyn Maw on June 23, 2011, no comments

This is a monostable multivibrator circuit, or “one shot”.  The diference between a monostable and astable multivibrator is that the monostable vibrator has a default or preferred state from which it can be jostled for a only a set period of time. That time frame is determined by C1 & R2, see information about the RC time constant.  In this circuit applying voltage to the trigger T will ground one of the leads of C1, causing it to behave like a short until it can charge again via R2.  Q will read as voltage high during that period. It is normally off.

 

Again one of the sites from yesterday has a good write up:
but compare it to the circuits on these two pages:
Niether use the extra transistor, but instead apply a switch straight to the base of Q1. The capacitor on the first links page makes it nonretriggerable, I think.

Eagle 30/30 No. 20 – Hand-Gun Sensor Mic and the Ground Plane (LM386 v0.1.b)

by Carlyn Maw on June 21, 2011, no comments

There is this succinct tutorial from Muzique.com. TL;DR and Notes from me
  • Use the polygon tool on the copper layer you want the plane to be on. It can be bigger than your board outline, Eagle will trim it.
  • Name the polygon GND or whatever your ground net is called with the name tool
  • It will be just an outline until you hit the Ratsnest button, can undo that by “ripping up” the polygon
  • The next time you open the file it will be hollow again. Add the RATSNEST *; command to your eagle.scr file if that bothers you. (ripup @; if the reverse bothers you)
  • Change the default “isolation” setting for the polygon (in the Info panel) to give traces some extra room. I use the same width as the traces I’m routing, but 0.012 is a good minimum. 
  • To hide power wires while routing everyone else RATSNEST ! GND VCC  (if those are what you called those nets )   
  • RATSNEST * to make sure everyone is showing again (check out HELP RATSNEST for more fun tricks)

There is some talk that OpAmp / Power Amp circuits don’t like ground planes in some circumstances… I’m not sure if this is one of them. Some articles say they are good for amplifiers, lots of discussion boards with smart people seem to say the opposite.  I actually put my signal wire on the bottom copper, poured the ground plane, ripped up the signal wire and rerouted it on the top. The problem is that this doesn’t hold from one day to the next (see bullet 4). Putting some wire lines on brestrict (layer 42) would keep the plane from pouring there. However, this may be exactly what I shouldn’t do.  I clearly need to read more. Henry Ott seems to be ‘the man’ for the Grounding of Mixed Signal PCBs subject and Mr. Ott says no slots!

Second:  Where did this circuit and the component values come from? How do you use it?

This circuit came from:

This table is to try to help clarify a little bit about the part values in the circuit. In this circuit VCC is a regulated 5V supply. That is not always the case with amplifiers, it is just that this one is for using a mic as a sensor for an Arduino.

Component

Phys Comp

Prac. Inv.

Evil Genius

Notes

R1

1K Ohm

N/A

N/A

Will change depending on the mic a bit. Think voltage divider with a low impedance mic on one side of it (the data sheet of the MD9745APZ-F says 2.2K Ohm, Mnf Page: Knowles) ) 

C1

4.7 uF

N/A (10uF in other amp circuits)

2.2 uF

None in the Smokey,as low as 0.01uF in other lil amps. This is the coupling capacitor, it passes AC while filtering out an DC background noise. It is also an initial signal noise filter, so keep that in mind if looking at a particular frequency range.

VR1

10K Ohm

10K Ohm

10K Ohm

Volume

R2

10K Ohm

10K Ohm

10K Ohm

R2 and C2 together change the gain from the default of 20 to basically whatever you want between 20 and 200. This is the 200 version. 

 

C2

10 uF

10 uF

10 uF

C3

N/A

0.1uF

0.05 uF

C3 & R3 together “Output Sound Shaping”

 

R3

N/A

10 Ohm

10 Ohm

C4

N/A

to GND

0.01 uF

Pin 7, the great mystery. Seen everything from this 0.01 uF to 47 uF in the Smokey Amp. This seems to be the the way to create pass filters for the data (big caps for low pass/bass, little caps for high pass/treble) Audiophiles use this pin for Hum Reduction

C5

220 uF

250 uF

220 uF

Also a filter – Up for more bass, down value for less bass. Also a coupling capacitor whose value technically should be 1/(2πƒR) where R is the load Resistance and ƒ is the cuttoff frequency (Prac. Elec. p 622)

R4, R5

100K

N/A

N/A

These two are shifting the line level back to the middle of the Arduino’s 5V range. 

C6

N/A

N/A

N/A

1000 uF is seen on Amp power supplies a lot. Including the SparkFun board. Depending on the rest of your circuit it may be overkill. If you don’t have one you can try with 33 uF or 100 uF…

IC1

LM386-1

LM386

LM386

If this to be used for the Arduino, must be a model that works with only 5V supplied to it.  The can be less noisy, though, the more power they are getting.  If you are thinking of using a different IC read this Electronix Express write up on Audio Amplifier Basics.

Secondly, interpreting the signal data. In one of the links I posted yesterday the writer rectified the output to make the coding easier. This will loose data as each of those diodes has a voltage drop associated with it. Better to fix it in software. 

The signal of the microphone is AC so the values the chip’s ADC sees will swing “wildly” across the midpoint determined by the line leveling part of the circuit (R4 & R5). Determine what the midpoint is (around 512-ish) and either ignore values below it or check for either amplitude extreme: 

s = analogRead(A0);
if (s > 700 || s < 300) { do(the_thing) };  

There are other things besides threshold checks that can be done, like frequency counting, etc, but just checking the amplitude data will get the “Did someone clap?” question answered.  Changing the capacitors on some of the filters might make it more of a “Did someone whistle?” or “Did it thunder?” but audio circuits are not my strength.

Eagle 30/30 No. 19 – LM386 Audio Amplifier w/ Electret Microphone as Sensor, v0.1

by Carlyn Maw on June 20, 2011, no comments

Doh. Missed the cut off by a tinsy bit to go see Submarine directed by Richard Ayoade of “The IT Crowd” fame.  Totally worth it.

More on this one in the future… it’s a combo of the standard ITP version and some other circuits. To see the Physical Computing, pg 357 circuit you can go here:  http://itp.nyu.edu/physcomp/sensors/Reports/CondenserMicrophones – although I’m wondering if the rectifier is truly necessary, I’m wondering how using the bypass cap would effect it the behavior… and if looking fo a threshold… why not do it in code?

LOOONG answer to “what’s a bypass capacitor”  :  http://www.intersil.com/data/an/an1325.pdf

Misc Useful Links: