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PostPosted: Feb 8th, '12, 16:45 
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I use TinyCad.
It's free and OK for quick schematics.
Libraries are a bit limited though, but it is quick to make your own parts.
http://sourceforge.net/projects/tinycad ... t/download
I think there's a Linux version too, called LiniCad.

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PostPosted: Feb 8th, '12, 18:04 
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Seriously, this cant be healthy.
Seriously, this cant be healthy.
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cool, thanks

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PostPosted: Feb 9th, '12, 08:58 
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Seriously, this cant be healthy.
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So I bought a L293B H-bridge motor driver chip, and a handful of 08m pickaxe chips to replace the cooked one, but looking at the spec sheet I have no idea what the thing even does :)

didn't someone say this stuff wasn't beyond me!

So if anyone's feeling generous, (DuiNui :)), can you talk me through it rather than just telling me what to do.

I've searched for stuff online, but nobody seems to be doing what I'm wanting to do. Almost all of it is for 12v to 110v or for stepper motor control.

Also, looking at my air pump, it doesn't look like a very efficient design. The lever rests against the outside edge of the diaphragm at rest, and is stopped by that same edge on the "attract" stroke, so basically the "attract" stroke does nothing. They have mounted the diaphragm on a slight angle to avoid this I think, but on this one at least I dont think it's worked very well. The magnet sits around 2mm away from the coil, and the repulse stroke sees the diaphragm being bent sideways a bit rather than just moving straight out at the centre. This seems to me like it would add a stack of friction.

I wonder why they put the lever on the thing in the first place rather than just turning the diaphragm 90 degrees and sticking a magnet in the centre of it so the coil acts on it directly. Although having just said that, I think they are bringing the other pole around to the front U magnet style to act as a pull when the coil bit is doing a push.

Who knows, but it looks like this...

Attachment:
120 Things in 20 years - Electronics - 12 Volt AC air pump.JPG
120 Things in 20 years - Electronics - 12 Volt AC air pump.JPG [ 117.54 KiB | Viewed 3905 times ]

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PostPosted: Feb 9th, '12, 10:41 
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http://www.botskool.com/tutorials/elect ... r-h-bridge

Quite a nice description of what it does, how it does it and examples of different connections.
Think of it like a solid state toggle switch (which is pretty much what it is)
With the switch in one position you have +12V to one side of the coil and 0V to the other.
When you throw the switch the connections are reversed.

I've never used one myself, but I think you should have 2 control lines from the PIC and have a small delay between switching one pair off and the other pair on, otherwise there is a risk of having all 4 switches on at the same time, albeit not for long, but probably best avoided.

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PostPosted: Feb 9th, '12, 12:23 
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Seriously, this cant be healthy.
Seriously, this cant be healthy.
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thanks

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PostPosted: Feb 9th, '12, 18:39 
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BW start out with sorting out the code on the micro and getting the H-Brdige chip wired up properly. Then post the schematic here.
Do you have a scope ? Its ok if you dont, you could test the output on the picaxe is correct using 2 LEDs, on on each output, you should be able to see them flashing in turn.

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PostPosted: Feb 9th, '12, 21:03 
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Seriously, this cant be healthy.
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OK I'll post something up when I understand what I'm supposed to do with this chip :)

No scope, but the picaxe software has a sim for the pins and variable, and LEDs are my only friend :)

One of the first things I did was make LED+resistor pairs for my breadboard

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PostPosted: Feb 10th, '12, 20:00 
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nice, that should get you going :)
test it at a lower frequency, then when it seems right scale it up :)

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PostPosted: Feb 10th, '12, 21:31 
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I made a scope today with a PIC.
500KHz sampling, good enough for most hobby projects.
Total cost about $10.
I do miss my TDS-220 though, for the money (at the time) that was an awesome DSO.

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PostPosted: Feb 10th, '12, 23:33 
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็ัShow me your oscilloscope please.


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PostPosted: Feb 10th, '12, 23:48 
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It's just a bit of prototype board with a PIC24F16KA102 on it, connected to a PC via a 1Mbit serial link to some VC++ Software.
I'll take a pic and a screenshot tomorrow, I'm on the laptop now, just turned all the other stuff off for the night.
Beer Time :)

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PostPosted: Feb 11th, '12, 04:54 
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DuiNui wrote:
I made a scope today with a PIC.
500KHz sampling, good enough for most hobby projects.
Total cost about $10.
I do miss my TDS-220 though, for the money (at the time) that was an awesome DSO.


I thought you were supposed to be setting up GBs ? :D
Nice work though, have you seen the micro based kits available ? just google DSO

I bought a RIGOL 50MHz for about $450 on ebay I think. Its no Tektronix but its actually really good.
The best scope I have used are the Yokogawa scopes. Beautiful interface, many options, just a dream to use. My previous workplace got 2nd hand ones for around the $7-10k mark. WAY better than the current model Agilents ($15k) IMHO

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PostPosted: Feb 11th, '12, 08:20 
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I have one of these. Which i got for free. :)

http://www.home.agilent.com/agilent/product.jspx?nid=-536902796.536880783.00&lc=eng&cc=AU

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PostPosted: Feb 11th, '12, 09:13 
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SuperVeg wrote:
I thought you were supposed to be setting up GBs ? :D

I got one done!
Not been too well lately so not done much physical stuff.

rsevs3 wrote:
I have one of these. Which i got for free. :)

Free is a most excellent price :)

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PostPosted: Feb 11th, '12, 11:39 
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Spec sheets should start with the words...

"If you stick 5 volts in this end, and 20 volts in this end, etc."

I dont know what everything means!

I'm looking at this...

Attachment:
L293B.jpg
L293B.jpg [ 40.46 KiB | Viewed 3819 times ]


and this...

Attachment:
ratings L293B.jpg
ratings L293B.jpg [ 37.75 KiB | Viewed 3820 times ]


And there are a lot of things I dont understand.

For starters why are there so many ground pins? cant they be shared?

Am I looking at connecting a PWMout PICAXE pin to set input 1 (pin 2) on the L293B to high (+5volts) to make 12Volts blerg* out of output 1 (pin 3), then sending a pulse to the other side (pins 14 and 15) then repeat?

And if thats the case, what do I connect to Logic supply voltage? That sounds like the output of my PICAXE chip but is rated to 36 volts.

7 volts sounds more like logic stuff.

And why are there so many grd pins?


*to emerge in a useful manner

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Last edited by BullwinkleII on Feb 11th, '12, 11:43, edited 1 time in total.
crazy picture size irritating everyone


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