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EEVblab / Re: Solder Fume Extractors
« Last post by cdev on Today at 01:38:54 PM »
The best fume extractor is the register for the return on a heat recovery ventilator.
Across the board, i avoid Safari on the pad and phone (Chrome)
To the poster that suggested Tapatalk... to each his own.  Never again for me, I tried it and was totally unimpressed.
Which DDS would you recommend?
What sort of voltage and current?  What sort of positioning tolerances can you guarantee between the two connectors?  If your drawer has close enough tolerances to guarantee connector alignment as the two halves are mated, then you can use just about anything.

If you can't guarantee that kind of alignment through the drawer's mechanics, you may want a "blind mate interconnect".  These have features that help guide the connector housings into alignment before the contacts begin to mate.  An example would be Molex's Mini-Fit Jr series, which includes BMI variations, although only with 4+ positions. 
plug housing--note how the slopes around the connector face help guide the mating connector into position.
receptacle housing

You could also design mechanical features around a more conventional connector to accomplish the same thing, although of course you need to make sure the alignment of those features to the connector is good enough.

Another option would be to use spring contacts.  There are some contact blocks designed for connecting to removable battery packs that may work.  If you use one entire block for each of your two connections, then you can have them mate with a single big pad on the other side so that left/right-up/down alignment isn't critical--although such contacts often don't have a very large range of motion, so front/back alignment will still need to be fairly close.  There are these from Mill-Max, or go here and look through the spring-loaded connector options.

Oh i forgot to mention, my voltage and current requirement is around 24 V and 3 A. I think I can guarantee misalignment within 1 mm but of course if there is some connector that can tolerance greater it would be great for me. I'm looking for something that can easily installed lets say just using bolt and nut or simply snap in place.

I think this product might work for me. So for plug i just need to make square hole and for receptacle a square hole and 2 holes. Is this kind of connection good enough for long term use? This drawer will be opened and closed frequently. For wire, is it crimped like in ATX power supply connector right?

For now I think I just want to buy connector and install it in my design. It will save me hassle modifying connector :D

My friend once suggested me with spring loaded contact but i'm still not quite understand how to install it in my drawer. Is it require PCB to mount this spring loaded contact? I try to avoid making PCB for this.

Use the draw slides as your contacts, and have a micro switch at the back to break it, this way your garenteed to always have good connection (provided low voltage and low current)

I don't think its a good idea, all of drawer will be made entirely from metals.

Thanks for your suggestion guys
Projects, Designs, and Technical Stuff / Re: Winding a 4 gauge inductor
« Last post by Ian.M on Today at 01:22:19 PM »
The penalty for shimming a square center leg to have half-rounded end pieces is 28.5% extra wire length, increasing copper cost and resistive losses in the same proportion.  However you probably don't need full half rounded end pieces.   About the smallest radius corners that would be windable would be 1 wire diameter radius.   I believe from your photos the E lams are 2 1/2" across the center leg, and 4AWG wire is approx 1/5" diameter.  Allowing for insulation, a 1/4" radius should be acceptable, and, assuming a square center leg it will only add 5.7% to the wire length required.

You certainly shouldn't be trying to wind straight onto the core. A former or mandrel is essential so you are only trying to bend the wire in one plane.   If you are winding on a former the mandrel is essential to support it to withstand the crushing forces while winding .  Ideally you'll want a split hardwood mandrel (with the split on the slant and both pieces waxed and highly polished) so when you move the halves in opposite directions to unwedge it, it separates from the coil or former easily.  If you aren't using a former, either groove the mandrel faces or prepare the mandrel with lengths of linen cord with the excess taped down away from the winding area, so you can tightly tie (and glue) the wound coil to stop it springing apart when you remove the mandrel.

I did say in your other topic, that I'd probably choose to wind such a heavy coil from thin copper sheet (or heavy foil), one turn per layer, interleaved with Kapton tape for insulation.  The depth of the E looks to be about 3 1/2", so to get the same CSA as 4 AWG wire you only need 10 mil (0.25mm) foil.   Assuming Kapton tape of 0.1mm total thickness, you should be able to get over 80 turns on.
HP 3326 dual oscillator - 13MHz can be either different phase or frequency.

Are you sure it's not a kit? It immediately reminded me of:


I was given that kit, I believe that it was the EE20, probably around 1968. I wonder how many people on the forum were influenced by these kits. I seem to remember two kits, a base kit and an expansion kit.

I also had a Philips radio kit. This kit didn't use the springs, it had a grid of nuts an bolts molded into the bottom of the case.


EEVblab / Solder Fume Extractors
« Last post by W8LV on Today at 01:15:23 PM »
I see Dave uses a "Pace" Solder Fume Extractor...
And I see, on the market, two basic types of extractors: The Computer Fan with activated carbon, which is cheap... And the "Hose and Box" types, which are HEPA and Carbon Filtered. And they are EXPENSIVE!

Looking hard, I only find Solder Fume Extractors in these ranges.

I'm going to assume that the HEPA/Carbon types are superior: Fine Particles removal (by HEPA) and toxic gas removal (by carbon). A Gas mask, essentially.

What I don't understand is how they should be so expensive. The cheapest "box and a hose" type I see is the "Hackker" job: Over Six Hundred US Dollars upfront, PLUS about One Hundred Dollars just to replace the filter... And that's just too much! I can buy HEPA/Carbon filters for home air units at Wally World for about ten to fifteen dollars for the home room air units at Wally World, and I've got this feeling that fiberglass pleated paper and charcoal just shouldn't cost a hundred dollars.

Certainly, there MUST be a cheaper box and fan type coming from somewhere, and I'm just missing it along the line. Does anybody know of one? 

Sent from my SM-N920V using Tapatalk

As for the counting methods, the easiest way would be a tiny DC motor with a contact reading the revolutions into a uC's counter input.  No comparators, no op-amps, no fancy voltage-frequency converter ICs, an almost all mechanical solution except for the uC counting the motor's RPM.
General Chat / Re: Arduino projects, a little suggestion needed
« Last post by Rerouter on Today at 01:13:50 PM »
As someone a decade down this rabbit hole, the best thing i can suggest it keep building things that are slightly outside your comfort zone,

Most of my knowledge developed from me trying to do something in a way that now seems very foolish, but it meant i learned the how and why the better alternatives exist.

One of my first involved arduino projects that I approached was dumping a bank of parrellel roms from a bit of test equiptment i was trying to repair in case i later bricked it.

Now this definatly doesnt set the tone for the complexity you need to meet, it was an example of i needed to do something suited to a microcontroller and early on i had enough free time that me playing around for 6 hours with shift registers was better value than a $160 eeprom programmer.
One thing I discovered was that the math I borrowed from other posts is not making use of the atmospheric temperature at all

Not sure I understand. The spreadsheet does use atmospheric temperature entry. Air_Temp in K is converted to AtmC in C which then used in the formula for h2o parameter. Is it the spreadsheet using named cells vs cell coordinates that confuse you ?
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