All About Circuits Forum - Blogs http://forum.allaboutcircuits.com/blog.php A discussion forum for electronics and circuits en Wed, 16 May 2012 23:43:21 GMT vBulletin 60 http://forum.allaboutcircuits.com/images/misc/rss.jpg All About Circuits Forum - Blogs http://forum.allaboutcircuits.com/blog.php RC time formulas http://forum.allaboutcircuits.com/blog.php?b=485 Wed, 09 May 2012 22:51:08 GMT Just versions of the same formula solved for each part. For the sake of avoiding mistakes caused by doing the math each time you need a formula. ... Just versions of the same formula solved for each part.
For the sake of avoiding mistakes caused by doing the math each time you need a formula.

Vo = dV (e^-t/RC)
t = -RC Ln Vo/dV
RC = -t/(Ln Vo/dV)
R = -t/C (Ln Vo/dV)
C = -t/R (Ln Vo/dV)
dV = Vo/(e^-t/RC)
e = 2.71828183
Attached Thumbnails
Click image for larger version Name: RC Time Circuit.png Views: 326 Size: 2.4 KB ID: 262  
]]> #12 http://forum.allaboutcircuits.com/blog.php?b=485 Regulated breadboard powersupply http://forum.allaboutcircuits.com/blog.php?b=484 Wed, 02 May 2012 07:27:15 GMT I got inspired by one of the threads on the forum, and that ended up with this. My way of making a workbench/bread board powersupply. The input... I got inspired by one of the threads on the forum, and that ended up with this. My way of making a workbench/bread board powersupply.

The input source is a wall wart 30v 1.5A.

It's limited to regulate down to 12vdc and 5vdc. Nothing more and nothing less.

I design my schematics in Eagle, here is the schematic:

Click on image for bigger view.


... and a panelized version of the board layout:


The process:

After the design is finished, and I'm satisfied with the board layout, I print it on transparent sheet. Twice. This way, when I put them on top of each other, the UV-light is completely blocked. After development, it leaves a nearly perfect result. Next is the etching. That's done in Ferric Chloride. I've made my own agitator, to speed up the process. I could also heat the etchant a bit, but I don't do that. It's around room temperature.


When etching was done, I sanded the board with super fine sand paper, and cleaned it with Acetone. Both sides. That also removed the rest of the photoresist that was left. Next I drilled a hole to hang the board up while painting. I've bought some paint. This type from Bungard I painted both sides, and was a bit excited about the solder side. Would the paint do it impossible to solder? Well, it didn't. I was easy to solder this.



The finished pcb and solder product.
I think it looks really nice.

Here's some better pictures.


Disclaimer:
I take no responsibility for what others might do with the schematic, circuit or paintjobs. This work for me, though the schema and circuit might not be 100% efficient or optimized.
Attached Files
File Type: zip Regulated Powersupply.zip (101.8 KB, 55 views)
]]> nerdegutta http://forum.allaboutcircuits.com/blog.php?b=484 <![CDATA[Boeing's JTRS program]]> http://forum.allaboutcircuits.com/blog.php?b=482 Tue, 10 Apr 2012 23:53:40 GMT Classic top down engineering. Put the people with the smallest understanding of the technical issues in charge of designing the "big picture" and then let those little engineer folks work out their silly problems. This is a consistent problem in corporation based product development. Until the baby boom MBA's retire and go away it will always be this way.


http://www.iwatchnews.org/2012/01/10...-perfect-radio ]]> tomshong http://forum.allaboutcircuits.com/blog.php?b=482 Panelizing in Eagle. http://forum.allaboutcircuits.com/blog.php?b=481 Sun, 29 Jan 2012 10:12:13 GMT When you design a board, you might want to have a few exact copies of it. In Eagle, there is a way to make multiple boards, on one sheet of paper or... When you design a board, you might want to have a few exact copies of it. In Eagle, there is a way to make multiple boards, on one sheet of paper or transparent.

This is the way I do what is called Panelizing.

1. Design the board
First things first. While making the schematic, I have Eagle Board Editor on the second screen. That way I know the footprintsize once the component is placed. When schematic is done, and the PCB layout is OK, I close the Eagle Schematic Editor.

2. Saving
So we don't mess up the original schematic and board, it is necessary to save our work under a different name. Both the schematic and the board.When I save, I use -pan after the name. I was working on a project and needed multiple boards, I saved it as 555-pwm-pan.sch. When designing the board and making a prototype, I named it 555-pwm.sch. So in the project folder, there are now 555-pwn.sch, 555-pwm.brd, 555-pwm-pan.sch and 555-pwm-pan.brd.

Delete the *-pan.sch file. NOT the *.sch or the *.brd files. These are our original files, and we do not want to mess with those.

3. Run panelize.ulp
For the panelize-ulp to work on all layer, we must show them. Click on the layer button, and on all. Now all the layers should be visible, and show all kinds of stuff. Now it is time to run the ULP. Click on the ULP - icon, and navigate to the panelize.ulp. It should be where the rest of your standard ULP's are. When panelize.ulp starts, it displays a message, click on execute. You notice that the names of your components have turned yellow.

Now you need to mark everything. Just like when you are moving two or more components. Click on the Mark - icon and mark the entire board. You will see that the board is highlighted.

We have now marked everything, next thing to do, is to put what we have marked in a buffer. This is actually a bit strange but, click on Edit, click on Cut. And now you need to tell Eagle where the boards basepoint is. I use the lower left corner. Click on that corner. Now we have placed a copy of our board in the copy/paste - buffer, with an reference point.

4. Placing the boards
Now all the tricky parts are done. All that is left is to place our copies. Click on Edit and Paste. You will now get a copy of your board floating around in Eagle Board Editor, with the lower left corner as an referent point. This copy can be rotated just as an ordinary component. Place it and use Edit -> Paste, to get a new copy.

The only limitations you have, is your version of Eagle.

5. Summarize

Save
Save as... (*-pan.brd)
Delete *-pan.sch (if it is there)
Exit Eagle Schematic

Show all layers
Run panelize.ulp
Mark all
Edit -> Cut
Click on reference/base point (lower left corner)
Edit -> paste.
Place new board.

Repeat Edit -> paste.

Repeat until you have reach Eagles limitations, or you have enough boards.


This is the way I get multiple Eagleboards on one sheet.

...Or you can drop me a *.brd, and I'll see what I can do...

My setup are:
Ubuntu Desktop 10.04 LTS
Eagle 5.7.0 - Hobbyist Licence.
... dual monitors

Disclaimer:
This is the way I do it. I will not take any responsibility for what others might do. Be careful and not delete the original files! ]]> nerdegutta http://forum.allaboutcircuits.com/blog.php?b=481 A 16+16v 1.67A Constant Voltage/Constant Current Lab PSU http://forum.allaboutcircuits.com/blog.php?b=480 Tue, 13 Dec 2011 21:31:20 GMT
This project is licensed under a Creative Commons Attribution-ShareAlike license (essentially, it's free to use for any purpose, but any modification must also be shared the same way). See the footer for details.



This Lab PSU is based on the one displayed in the LM317 datasheet, named "5A Constant Voltage/Constant Current Regulator", shown here for reference:



As you can see from the version in the datasheet, -6v are needed to allow the opamp to pull down the output of the LM317 to 0v in case of a short-circuit scenario, so i decided to use a 15+15vac 3A transformer (in fact, i already had it, it should be possible to go to 20+20vac, using a beefier heatsink), and built also a negative version of the circuit, so that it can be used to test amplifiers and other circuits requiring a split supply. The transformer must have 3A, as they lose efficiency when not supplying a resistive load, and a rectifier w/capacitive filter has nothing of resistive. It's recommended to not exceed the Amp rating divided by 1.8 for this kind of load.

I kept the voltage and current at reasonable levels. 35v and 5A as seen in the datasheet are simply not possible, as they would kill the LM301A (36v absolute maximum supply voltage, but 41v applied here). The LM101A or LM201A would withstand it, however. Anyways, no single transistor will survive 35v x 5A = 175 watts of power disipation, so there's no way unless you want to use several power transistors and a huge heatsink. When needing so much current, a variable linear design is not the best idea in the world, anyways.

I also changed the transistors for newer versions, modified the voltage regulation area to go near 0v, and moved the 1uF capacitors closer to the input of the LM3x7 to avoid some unstability problems that i detected when working in constant current mode. I used the TO-220 version of the regulators, i see no point on using TO-3 regulators, like suggested on the original circuit.

I also named the project "Open Lab PSU", and put it under a Creative Commons license (details in the footer).

The PSU consists of 3 small boards: the rectifier board, and the positive and negative boards.

The rectifier board
The rectifier board has the rectifier, capacitor bank, and +6v and -6v regulators.



The positive board
The positive board has the positive regulator and current limit circuit.



The negative board
The negative board has the negative regulator and current limit circuit.




Issues
To the date, the only issue i detected, is that the positive board has ripple in a very definded "grey area" between CV and CC mode. For example, the following image shows the worst case detected of 53 mv peak-to-peak ripple when the PSU is configured to limit on 12v 0,8A over a 15Ω resistor (just on the verge of current limit):



Raising or lowering the current limit by 20mA out of that zone gives the following readings:




Build details
I mounted both power transistors with mica insulators and thermal compound to the same ZD-2K heatsink, it has a thermal resistance of 0.92 °C/W. If you use a bigger transformer, you need to recalculate the heatsink for safe worst-case scenario operation. Also modify R6, the 2k potentiometer and/or R1 for a different voltage/current limit.
I put 6225D heatsinks on the LM3x7 regulators. They have a 10°C/W thermal resistance, but they're overkill, you can use 20°C/W.
About the fuses for the mains side, it varies by country. I have 220v here, so i used a 1A fuse (90VA transformer rating / 220v ~= 0.4A). All fuses must be of slow-blow type, because the inrush current is high.
I still didn't decide where to put the fuses on the low-voltage side. Putting them before the rectifier board seems to be the safest, but the capacitors will charge at great currents on turn-on, so slow-blow fuses shoud be used. Normal operation is up to 1.67A, so the fuses must probably be the next bigger value. Not tested, however.
Another thing to note, is that the red leds aren't soldered into the board directly, they go in the front panel. I soldered polarized "power" connectors there, but decided to keep the led in the schematic, because it shows correct polarization, and the pinout matches.
The current limit circuit is a high impendance input. I kept wires short and used twisted cable to avoid noise pickup.


The project is available in Cadsoft Eagle 5.11 format, attached in this blog entry.

Open LAB PSU by Fernando Rapetti is licensed under a Creative Commons Attribution-ShareAlike license. For attibution, a link to this page (http://forum.allaboutcircuits.com/blog.php?b=480) must be included on any derivative work. Note that you build this at your own risk, i would not be held responsible for any damage.

Attached Files
File Type: zip Open Lab PSU.zip (230.8 KB, 378 views)
]]> Norfindel http://forum.allaboutcircuits.com/blog.php?b=480 SMD soldering, first try. http://forum.allaboutcircuits.com/blog.php?b=479 Tue, 08 Nov 2011 20:58:05 GMT I've always thought that SMD soldering is hard. And I guess it is, when it comes to advanced circuits and SMD ICs.

I had my first try this evening. Both with SMD soldering, and etching with Ferric Chloride.

I've etched a few boards, and I've used Natriumpersulfate, at approximately 50°C. Lot of rigging and waiting and boiling.


First time Ferric Chloride.

Today I got my hands on some Ferric Chloride, and I gave it a try. It was much quicker than what I'm used to, and being careful with the safety, it was clean too. The ferric had just about room temperature, and worked like a charm.

Next question is: How and where to store it?


Board is scanned at 1200dpi, and scaled to 640


The procedure was quite easy. I tinned one of the pads, aligned the component, held it in place with some tweezers, and re-heated the solder. The component then sank into the solder and was fastened. The other side was just a short heating with the solder iron, and apply the solder.


Picture is taken with high resolution and scaled to 640.

Not bad for a first timer...

Now I need to figure out a nice and easy way to store the SMD components, because I am definitely considering starting with those. The size for these is 0805. And the outline of the board is 23 x 35mm.

A new era has started in my journey in the world of electronics...
]]> nerdegutta http://forum.allaboutcircuits.com/blog.php?b=479 Inductance measuring jig. http://forum.allaboutcircuits.com/blog.php?b=478 Fri, 21 Oct 2011 05:51:14 GMT I built this circuit while studying 1/2CV^2 = 1/2LI^2 The transistors I had were RCA brand 1B05 and the diode is a 2000 volt fast Trr diode. Set... I built this circuit while studying 1/2CV^2 = 1/2LI^2
The transistors I had were RCA brand 1B05 and the diode is a 2000 volt fast Trr diode.
Set the current by adjusting Vcc.
I used a single function generator to get a ttl square wave to allow current through the inductor under test, and simultaneously, the triangle wave, adjusted on the front panel, dumped the voltage for each cycle.
You size the unlabeled capacitor to get a reasonable Vpeak when the current stops. It was .1uf@200V when I used this circuit.

By using a scope to measure the current through the 10 ohm resistor and the Vpeak at the capacitor, you can calculate the size of the inductor.

Not elegant, but functional, and it can be cobbled together with junk box parts.
Attached Thumbnails
Click image for larger version Name: Inductor measuring circuit.PNG Views: 2912 Size: 8.8 KB ID: 257  
Attached Files
File Type: pdf 1B04_1B05.pdf (78.7 KB, 560 views)
]]> #12 http://forum.allaboutcircuits.com/blog.php?b=478 1N4000 series start time http://forum.allaboutcircuits.com/blog.php?b=477 Fri, 21 Oct 2011 02:27:06 GMT I saw this information on this site and decided to "blog" it so it would be easily available in the future. It is about the turn on time of the diodes and was originally posted about a snubber question.


Associated math goes like this: If you want to use a capacitor to help the SCR survive until the diode conducts, IT/V = C

Example for a 1N4007, (4 A x .6 usec)/200V = .012uf minimum. ]]> #12 http://forum.allaboutcircuits.com/blog.php?b=477 PCB board houses http://forum.allaboutcircuits.com/blog.php?b=475 Mon, 03 Oct 2011 16:52:00 GMT This is a question that comes to the board, from time to time. I decided to make a list over some PCB manufacturers. Usually a post starts with... This is a question that comes to the board, from time to time. I decided to make a list over some PCB manufacturers.

Usually a post starts with one of these questions:

"Where can I get boards done?"
"Who is best?"
"Which is cheapest?"
"Which is fastest?"
"Who can I trust?"

This is a listing of houses that makes PCB's, most of them are found in threads on the board.


And of course:

http://forum.allaboutcircuits.com/sh...ad.php?t=47681

And:
http://forum.allaboutcircuits.com/blog.php?b=450

The list is not in any priority. I've never ordered board from any houses. I've just made board with the last two entries.

This is a "work in progress". New board houses may be added, along with some comments. :) ]]> nerdegutta http://forum.allaboutcircuits.com/blog.php?b=475 Well, a stroke of bad luck... http://forum.allaboutcircuits.com/blog.php?b=474 Sun, 02 Oct 2011 16:53:38 GMT Well it looks like I won't be working on this project for a little while. I went out this morning to grab my bike from the rack, and found out it was stolen during the night. The robber cut right through the chain locking it to the rack. I have informed the police and am working on getting them photos so that they can file a report, and I'll be out looking myself. The bike was still in terrible condition, and I took out the rear brakes to work on it. With any luck, he'll just ditch it somewhere nearby where I (or the police) can find it again.

I guess it's not a huge loss, because I had removed the rack, motor, and other fittings before chaining it up. On the other hand, everything is sized for this bike and may differ a bit from other bikes.

I will keep you guys posted on the progress. Just be forewarned that it may be a different bike by the time I post again.

Thanks for reading, and I will try to work this out as soon as possible.

Der Strom ]]> DerStrom8 http://forum.allaboutcircuits.com/blog.php?b=474 Simple electric Motor http://forum.allaboutcircuits.com/blog.php?b=473 Fri, 23 Sep 2011 17:24:12 GMT Attachment 250 (http://forum.allaboutcircuits.com/attachment.php?attachmentid=250) This is one simple mini-project that based on the principle of...
Click image for larger version Name: vlcsnap-2011-08-31-14h39m07s179.png Views: 1021 Size: 126.3 KB ID: 250

This is one simple mini-project that based on the principle of Motor effect.we can clearly visualized the rotating effect when the magnetic flux of magnet is intersect with magnetic flux due to the supply current.


Apparatus required:

1) magnet
2) insulated wire
3) one box
4) power supply

Construction Detail:


Click image for larger version Name: Untitled-2.jpg Views: 769 Size: 153.0 KB ID: 256 Click image for larger version Name: Untitled-1.jpg Views: 684 Size: 158.3 KB ID: 253

  • Take insulated wire and make a coil of about 12 to15 turn and keep two end out in such a way that is properly balance.
  • make two stand by some hard wire that support coil.
  • connect this stand with power supply.
  • remove insulation of the half part outward projected insulated wire coil (that is connected with stand only in half rotation and half rotation is completed by mean of inertia. )
  • switch on the power supply and your project.
Attached Images
File Type: jpg vnvnvn.jpg (31.0 KB, 474 views)
Attached Files
]]> devgorkha http://forum.allaboutcircuits.com/blog.php?b=473 I missed my elementary days grade VI http://forum.allaboutcircuits.com/blog.php?b=471 Sat, 17 Sep 2011 17:49:40 GMT I really missed my Grade VI times even though we are only five students. I don't know why.;)

I am very happy when I was Grade VI.:DI really don't know why. I wish I could experience again the happiness I felt when I was Grade VI.:D

Now, in high school, there's so many curricular activities as academic activity is not the priority anymore, I guess.:)

I don't want to dance, sing, anything, please forgive me even in this criteria.:mad:I don't want to get 70% in MAPEH but I really don't want to dance, sing, anything. I want to do something academically. But ye, with some curicullar activities, OK.

Field trip, science, camping is OK and very OK but dancing, singing, cheering, etc not. Please I hope somebody would understand and not give me 70%.

I know you know I can't. And if ever I do what you command, our whole section will be a laughing stack. Do ya like that? Me, no. But I don't know why you're still forcing me to do what I can't.

I understood that it is needed. I also understood that the whole section must do. But I really can't. I am just one who can't, but the majority can.

I understood that if I won't do it is unfair that you give me 95% in grade or 85% rather. But I don't know.

I really need a school wherein curiccular activities is not not needed.

Grade VI is the best so far.

The Sad Catapult:mad: ]]> Lightfire http://forum.allaboutcircuits.com/blog.php?b=471 DIY Electric Bicycle, Entry #11: Building the Bike (The Rack continued) http://forum.allaboutcircuits.com/blog.php?b=470 Sun, 04 Sep 2011 17:10:49 GMT Continued... 5) After rigging up the support bar, I set the actual rack on it to see how it looked:... Continued...

5) After rigging up the support bar, I set the actual rack on it to see how it looked:

6) And after a bit of welding...

7) Now for the vertical supports. I decided to do what most professional bicycle racks do, and support mine on the rear axle of the bike. I took some strips of metal and drilled a couple of holes in them to slide over the axle:

8) And connected....


To be continued (still)... ]]> DerStrom8 http://forum.allaboutcircuits.com/blog.php?b=470 DIY Electric Bicycle, Entry #10: Building the Bike (The Rack) http://forum.allaboutcircuits.com/blog.php?b=469 Sun, 04 Sep 2011 17:05:03 GMT The following photos will show the construction of the rack which holds the motor and the battery. 1) This is the bar that will support the rack... The following photos will show the construction of the rack which holds the motor and the battery.

1) This is the bar that will support the rack and connect to the rear of the seat post:

2) I cut out some pieces from a sheet of scrap metal that could be welded to the bar. The "connectors" had little holes in them so that a bolt could be put through:

3) I test-fitted the connectors on the rear of the bike. I had to do a bit of filing to get them to fit nicely, but that wasn't a problem.

4) I then put the bar between them to see if the width was about right. It was close, and the welds would easily be able to fill the gaps.


Looks good so far :D

To be continued... ]]> DerStrom8 http://forum.allaboutcircuits.com/blog.php?b=469 DIY Electric Bicycle, Entry #9: Building the Bike http://forum.allaboutcircuits.com/blog.php?b=468 Sun, 04 Sep 2011 16:59:10 GMT To begin with, I'd like to mention that I found a relatively small 12 volt car battery out of a Volkswagen Rabbit. It is much narrower than a standard car battery, not to mention about half the weight:



For this reason, I think it will work well to power the bike.

Anyway, back to the bike construction...
The first thing I wanted to build was the rack, to hold the motor and the battery. I figured this would be one of the most important parts to build for this project, and also one of the easiest.
To start with, I needed to figure out how to connect the rack to the back of the seat post. I looked at it and noticed that there was plenty of room on the clamp that holds the seat:



It would be very easy to build a simple bracket to connect the rack to the bike. The following entries will show the process of attaching the rack. ]]> DerStrom8 http://forum.allaboutcircuits.com/blog.php?b=468