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Hand winding of helical springs?

Are there any thoughts on an easy way to hand wind a helical compression spring using simple hobby workshop equipment? Say, d = 0.25 mm, free l = 80 mm and shut force about o.5 N ( 0.1 lbf)

Question by Ozboat    |  last reply


Antenna for 434 MHz ASK RF transmitter module? Answered

Hi, I have these few questions regarding aerials that can be used with a 434 MHz ASK RF Transmitter module. https://electrosome.com/wp-content/uploads/2014/10/MO_SAWR.pdf  (data sheet of the transmitter) 1)The recommended length for the antenna is 17 cm,which is a quarter of the wavelength. Will using a 34 cm antenna(half wavelength) enhance the range of transmission? Will it get even better for 3/4 th and full wavelength long antennas? 2)Should the antenna be a monopole? Can I use a helical one instead(picture attached)? What are the ideal dimensions of a helical antenna(with respect to its wavelength) for maximum range ? Should the antenna of the receiver be of the same type or can I have a helical transmitter antenna and monopole receiver antenna ,both of same length? 3)Does Copper traces on the printed circuit board between the antenna pin of the transmitter and the actual antenna,add to the total length of the antenna? If the answer to the previous question is yes,can using coaxial cables to connect the antenna pin to the antenna prevent this from happening? 4)Should the antenna be installed perpendicular relative to the plane of the circuit board?Has it got anything to do with grounding or anything? Should the antenna be grounded too and if so how?(I am a bit confused with this part) 5)Can having the antenna in close proximity to step down transformers and ics ,produce undesired results?

Question by Adarsh_tronix    |  last reply


Obtaining helical slices from a 3D model

Hey guys, I've begun to work on a volumetric display for a school project like the one in the link at the bottom of this post but I can't figure out a good way to obtain helical slices of the 3D model which I intend to project. I could do it manually by subtracting the "negative" of the helical screen from my model in Solidworks and then take a screen shot, but this would be pretty time intensive since I would need 360 shots(360 2D images from below the model with the screen negative rotated one degree each time). Is there any program out there or add-on for solidworks which could automate this process? Or even a functionality in solidworks that I haven't thought of? Would appreciate any advice you have on this subject. Link To Helical Volumetric Display Video: https://www.youtube.com/watch?v=ihZ_mJ04U3c

Topic by Pyrowuzzup  


DIY WiFi Helical Antenna impedance Problems

First off, I live in the states, but I absolutely hate the imperial system of measurements. I will try to use the metric system as much as possible.I have been attempting to follow hanzablast's Helical WiFi Antenna, but have run into a few snags. I have most of the parts and have a few problems concerning it.1. Instead of a Type N connector my USB card has a RP-SMA connector. Do I have to do anything special (buy a special panel mount/ reverse the connections along the wire) because it has reverse polarity or does it not matter?Edit: I feel foolish, Doing a quick wiki search on Reverse Polarity SMA I found out what it means. Turns out WiFi companies reverse the gender of the inner pin in their connectors. So either I have to find a RP-SMA panel mount jack, or buy a RP-SMA Male to N Male Adapter and a N Female Panel Mount. The latter of the two seems more efficient.2. I understand that having too small of wire can have a detrimental effect on efficiency, but what about using a much larger wire (instead of AWG 16 gauge wire using AWG 4 gauge wire)?Edit: Answered By NachoMahma3. I am having trouble locating a SMA right angle 4-hole solder point panel jack mount other than in bulk buys. Does anyone know where to purchase one separately? Edit: Answered By NachoMahma, but has become a null point.4. I am having a problem with the impedance matching. I have seen several different ways to connect the antenna (142.68ohm impedance) to the SMA Jack (50ohm impedance). I've seen half and quarter circumference turns, quarter wavelengths turns, and triangular strips of copper. Which is best?Edit: I did the math and read my friend's ARRL handbook. Supposedly, a 1/4 wavelength turn of a metal strip with an impedance of 84.463 ohm is what I need. Using TraceSim I figured that I can use part of the copper plate with a size of 12.79033mm in width, 30.775mm long (1/4 a 2.437GHz wavelength), and 0.406mm (.016") thickness placed 8.03mm (1/4 distance between coils) above the reflector plate will give me the exact impedance I need.

Topic by AllAgainstPaul    |  last reply



Simple electrical insulation question. Answered

If I have a 10AWG insulated solid copper wire and the THHN insulation is rated for 600V, should I worry about a 5000V 60ma current arcing straight through the insulation if its coiled in a helical form?

Question by imMrDude    |  last reply


USB WiFi Antenna Mod

I am working on adding a helical antenna to a cheap USB WiFi adapter.  My question is where do I connect the antenna to existing circuit.  I've attached a closeup picture with three likely points.  My three main questions are: 1) Where to connect the external antenna 2) Do I disconnect the rest of the onboard antenna (my gut says yes) or just add in the new 3) What impedance will the external antenna need to match?  I assume the components between points C&B; and B&A; are for some kind of impedance matching.

Topic by telfon    |  last reply


Power source for running three 2000rpm gear motors?

So I have built a rover drone (instructable coming up soon) and the major problem is I don't know what power source I should use. It has three 2k rpm gear motors, an Arduino and a raspberry pi. Would a lipo suffice this? or should I use something else? Image source: http://imshopping.rediff.com/imgshop/800-1280/shopping/pixs/4463/5/507._6mm-gear-motor-1000-rpm-helical-for-diy-projects-dc-12v-1000rpm.jpg

Topic by droiddexter    |  last reply


Verticle Axis Wind Turbine Materials?

I've been working on a vertical axis wind turbine that uses uses 3 identical helical blades positioned around a central vertical axis. For small working models I've been using 16 gauge wire and cardstock. I'm looking to build one with 6-8 foot blades. The trouble is finding an ideal material for this. It needs to be lightweight, cheap, flexible, "malleable" (it needs to be able to be bent into a helix but then retain the shape), and come in a 4'x8' sheet. PVC/CPVC is super expensive, as is polycarbonate, and aluminum. Any suggestions? 

Topic by FLskater3696    |  last reply


Cloning the famous ARA-2000 antenna for SDR use

Several years ago the company behind the original ARA-2000 antenna, Dressler Hochfrequenztechnik, closed.The ARA series of antennas, like many other products by this company never got a patent, instead it was trusted that no one would bother to replicate it.A bit like the Swiss Army knife, many tried to copy it, none really managed to match the original quality.There is quite a bit of hacking still going on for this antenna, most projects though seem to be abandoned at the time of writing this.I am currently trying to figure out how to create an entire clone that everyone who knows how to properly use a soldering iron can build.There is a lot to consider here...The active element is of quite unusual shape and needs to be wound around a cylinder of a pretty accurate diameter.My initial tests showed that for example aluminium foil with some unavoidable wrinkles already has a negative effect.And a change in diameter of just 2mm means the entire antenna only performs badly for the entire band.This part is thankfully already solved to my satisfaction using thin copper sheets and some stiff plastic sheet.Quite a pain though is the MMIC part - the amplifier that makes the antenna active.There is a ton of MMIC blobs available, either solo or as a ready to go amplifier.Downside is that without really knowing any characteristics of the original is comes down to guesswork.And as most of the cheap SDR dongles won't provide a BIAS TEE I will opt for an external power supply for the amp.I might provide the option for a inline use a bit later though.Why clone the ARA-2000 antenna?For starters you need to forget the mythical stories you might have heard about this antenna."Picks up even the weakest signals!", "Totally linear over the entire bandwidth" and so on...Without the amplifier the antenna is actually not even average in therms of reception performance.My initial tests with a network analyser showed that the anteanna actually is behaving really weird (without the amp!).Although this first bit needs further testing, it seems that most, if not all of the work in the 1.5-2GHz range is done by just the straight connecting strup going from the amp, or in my test case the coax, to the wrapped antenna part.For anything in the more interesting frequency bands it seems that the antenna is not using anything like a discone, whip or ground plane antenna.Instead the 3rd harmonics of a given frequency provide the max power output from the antenna but it arrives at the cable at the right frequency.Especially in the lower frequencies, below 200MHz there is also quite some phase shifting happening.As a passive antenna it seems to be almost impossible to find a frequency to transmit on without using some matching trickery first.But when it comes to size or looks, the ARA outperforms everything you can think of unless you want to constantly adjust the length of your whip antenna.And if you check what is available in real (user) data in terms of noise and signal quality than most other antenna types are far worse.The design provides a wide frequency range with very little noise, almost like a build in filter.Considering that mostly harmonic frequencies are used not that surprising.Getting hooked on SDR means you start little and then you want more and more.Unless you really need the low frequency HAM bands below 50MHz the ARA is a good choice that just makes sense.What is quite surprising in the original is the total lack of protection for strong signals.Sure, we might never need a lightning arrestor because all is enclosed in plastic and has little attraction lightning, but someone hittiing the transmit button close by....I will have to do some more checks to determine whether or not more protection is required.What is the problem with amplifier?For starters, no one really knows what was used in the original - they all just guess based on how well the real design matches some datasheet.Means whatever was used might as well be a custom made solution.I checked a few datasheets for MMIC amps but could not find any useful reference to the handling of things like negative gain, phase shift or a constantly changing impedance.Some however state that a 50 or 75Ohm signal is provided at the output.If I interpret that correctly than those MMIC's not only amplify but also do some matching.In most cases you won't need an amp that works outside what the antenna can provide.Problem is that I don't like regretting things later on ;)So IMHO it would be best to use a wideband MMIC covering all from about 1MHz to a few GHz.Additional filters can then cut off what is not required or where the antenna starts to fail.What is clear by the original design is that the cable shield acts as a ground and most likely also has a balancing function.It would make sense to add a ferrite trap close the the receiver to filter out what the cable might otherwise mess up.Can the frequency range be lowered to get even the low HAM bands?The answer is YES and NO.It is not a big problem to extend the cone shape and then hope to come much lower.Issue with this is the helical, long periodic design.As basically only the 3rd harmonics are used for all interesting frequencies any ARA type antenna going much lower would end to be really long.You can't just make it longer!One thing is to have a full and even number of turns.The original only had two, three turns is bad, four means the entire antenna is slightly longer than your average downpipe for your roof gutters....Other, seemingly logical alternative would be to stick to two turns and to increase the diameter.Apart from the size problem here we would also change the shape of the foil quite a bit and I have not done enough tests with that to provide a conclusion.Are there alternative design options?As it turns out copper pipe is available in 80mm diameters for the use in chimneys as well as downpipes.With a proper machine it would be pretty straight forward to remove what is not used as the active element.Milling a pipe or rod is these days a common thing in many good workshops.But on a hobby level and low budget....One of the best options for cheap test antennas of this design is to use tinting foil - the cheapest you can find ;)Just read the lable and make sure it does not use a metalised film.If it has no UV protection and no tinit at all it is best but hard to find.A little less stiff is the stuff to cover school books or cupboards.Vinyl is bad though!If you look for copper foil in the cheap online places you mostly find the suff used for shielding in rolls of 200x1000mm.Unless you have a really sharp knife or really suitable sissors this stuff is a pain to cut as the glue tends to stick very good to whatever you use to cut through.Don't ever try one of these blade type cutters for paper and pictures unless you put a slight oil film on all cutting surfaces first....In some hobby shops you can get copper foil without any glue in different thicknesses - this stuff is the prefered option.Not only cheaper than the China rolls with glue but you invest a bit more and get a thickness that does not wrinkle right away when working with it ;)Cheap, steel downpipe and cutters or nibblers?I though about and I tried - and I failed LOLUnless you use a pin type nibbler and custom made rig the result is quite bad - at least mine was.What works though is to use thin aluminium sheets, cut them and then bend them around a suitable template.But I ran out of old laminated sings to salvage and the duble sided ones I have left are too much work.What comes next?Well, I have a few rolls of copper sheets coming next month, the cheap glue covered type.This time however I will leave the plastic cover on and use tape to secure the foil to the pipe.A two-stage amp with external power supply is coming too so I can do some more tests in this area.For the time being I will opt for some 3D printed end caps but with a bit of luck can find something easier next time I have time to waste in the hardware store.Excluding cable and a cheap USB or 12V power supply, the current costs of building the anteanna are around $40US.About half of that if you don't cennectors and attach the coax directly.Another experiement I am working on is to use copper tape, 12mm wide, to create the antenna in a semi-fractal style.I am hoping this will provide a high enough gain so the antenna is usable without an amplifier.Right now the biggest issue is to find a really SDR suitable way to deal with strong signal close by.I will keep you update here when I start with the new antenna and upload some pics along the was of building it.

Topic by Downunder35m    |  last reply