Recent Posts

1

Test Equipment / Re: TinySA Ultra launched

« Last post by shapirus on Today at 07:21:58 pm »

If you need that, you should buy a SG that does a true continuous sweep.

I never argued with this. I just said that if it could be fixed without compromising anything, then it would be nice and would benefit everyone. If it's not possible, then it's not really an issue.

2

Dodgy Technology / Re: ORIGAMI LOGIC, ? Yeah, sure, I'll try that!

« Last post by RJSV on Today at 07:21:55 pm »

   GOT MY BOOK  !!!
   Hello:
   My (Amazon delivered) Engineering Textbook, written by Bingim Young University Prof. Larry Howell is chock full of mathematics.

   Besides the obvious, helping myself in dealing with 'flexible' mechanisms, (like digital gates and transmission lines operating mechanically),
where I've contemplated a couple of historical trendy technology.   The particle or light 'beam' weapons (1985'ish) and the whole nanotech labled things (1995'ish) as examples.
I think some efforts around the special tech innovations occur quietly, as academia and industry maybe have less interest in sensationalism.
   One related product comes to mind; that is those single-piece plastic lids and bottle closures that closely reflect the discussion in that textbook.   So now I'm wondering at what point did that single example get introduced, present now in various retail candy containers we see on the shelves, as truly improved?

   As a short review, the Mechanical Engineering Textbook;
   Goes into matrix math, and Modulus of Elasticity.
   Solving simultaneous equations and advanced algebra manipulations, as part of the mechanics and physics analysis.
   Navigating between Sines /Cosines / Tangents and imaginary numbers.
   Concepts of virtual displacements and virtual work.

   Appendix containing data on various properties of materials and geometries of fabrication.

---------------------------------
   There are, also, some lectures by Prof Larry Howell, in directly related material (I.E. youtube).

3

Projects, Designs, and Technical Stuff / Re: Control of 2 CAN Open DS402 motors on a single shaft

« Last post by Simon on Today at 07:16:22 pm »

Yes that is about it. If I were to get this to work I would be able to sync more often as I my CAN Open master controller is no longer doing the speed regulation so it does not have to do anything with the data coming out at speed.

The Target_torque is the internal set point of the master speed controller motor. it will transmit on any sync message whatever the motor is doing.

The slave torque helper will basically use this as it's Torque_Demand (which will internally produce a torque_target that I assume will be the same) and so follow along.

The crux will be getting the torque motor to react quickly enough to fool the speed controlled motor into thinking that it has twice the torque or rather that the load is half of what it is as it will not be aware of the second motor. So the speed controlled motor will need to have a slower torque ramp rate than the torque control motor so that whatever torque it uses is quickly matched by the Torque controlled motor so that it does not see the full load. And hopefully this all happens without the two falling ass about face or oscillating.

4

Beginners / Re: Fast PWM IC

« Last post by langwadt on Today at 07:16:08 pm »

Is there any IC that could provide a PWM at 100 MHz or so? I would love to use atmega ICs but these go up to 20 MHz, if I am not mistaken. The idea is to use it for a voltage control in sample-and-hold circuit for short input pulses. Thanks!

100MHz pwm frequency or 100MHz time resolution?

5

Power/Renewable Energy/EV's / Re: 5 out of 6 vendors are scamming people with wrong crosssection of cables

« Last post by Stray Electron on Today at 07:16:06 pm »

   Where were the cables made?   Undersizing of wire and cables made in China has been widely reported on this and other sites.   A lot of the wire is also reported to be made some kind of junk alloy that isn't solderable.  I've learned to not trust the ratings of anything made in China.

I dont know, and the vendor wont tell me of course.

Only 2 of them were amazon and ebay (not chinese - and seemingls reputable ones), but the other had their own websites and did not have bad ratings. I think they are not aware of it either. One of them got quite furious, as he strongly insisted it was 6mm2 even though i told him two measurement methods showed otherwise (This one sold photovoltaik stuff).

Still my question is unanswered:
Have you ever checked on the cross section?

   I've never measured any that I'm aware of, but I've seen dozens of Chinese made wires and cables (including steel cable, aka "wire rope") that were obviously smaller than it was labeled.  Personally I haven't bothered to measure any of the Chinese electrical stuff because, so far, I've been able to buy reputable American made brands that I know that I can trust.  I've learned the HARD WAY, so whenever it's something that matters, I now go out of my way to good American, Japanese or western European brands even though they cost a lot more than the Chinese stuff.

   I DID look at probably 40 different lots of wire rope and I did measure a lot of it and ALL of the Chinese made stuff was much smaller than claimed.  Also I really have no idea what kind of steel it was made of so I finally bought 1000 feet of US made wire rope surplus.  My off road vehicle (1952 Dodge m-37) weighs almost 7,000 pound unloaded and calls for 1/2" IPS (Improved Plow Steel) wire rope that is rated for a 27,000 pound working load.  I found the stuff that the Chinese were selling was less than 7/16" and it BROKE at about 9,000 pounds. 

   it's the same story as my Chinese made trailer, it will almost meet the stated load but there is NO safety margin. 

6

Power/Renewable Energy/EV's / Re: 5 out of 6 vendors are scamming people with wrong crosssection of cables

« Last post by eTobey on Today at 07:15:25 pm »

No, because I order from Digikey/Mouser/Farnell.

When there are so many cases of wrong cross sections, i would be very curious not caring about big names.

7

Power/Renewable Energy/EV's / Re: 5 out of 6 vendors are scamming people with wrong crosssection of cables

« Last post by Bud on Today at 07:14:26 pm »

  A few years ago my 730 pound Miller welder got dumped unto the ground when the frame of my Chinese made 900 pound rated trailer bend under the load and within 30 seconds of placing the welder on it

Must observe the 11th Commandment: "Thou shalt downscale all Chinese specifications by a factor of 2".

8

Test Equipment / Re: TinySA Ultra launched

« Last post by erikka on Today at 07:12:18 pm »

If you need that, you should buy a SG that does a true continuous sweep.

9

Beginners / Re: What function generator, that does a bit more than just a simple signal

« Last post by eTobey on Today at 07:11:57 pm »

Please delete your offtopic when you have noted down those details.

You can also use PM instead.

10

General Technical Chat / Re: Russia and China to Build a Nuclear Plant on the Moon.

« Last post by GigaJoe on Today at 07:11:55 pm »

Have some fun ...

A cooling dome on the image at  the first post  ....  in the vacuum ...  is everything all right, I guess so ...

Then ...  each and every nuclear station on earth , fall under basic Carnot Cycle , where active body ,   transfer energy from hot side to the cold side, release energy, that transformed, and then cool down even more for efficiency,  by water or air cooling such as dome ....  That Carnot Cycle give you about 30-40% efficiency ,  the rest dissipated in a thin air. so -  1000 kW electrical nuclear unit about 4200 kW Thermal power, and 3000 kW dissipating as a waste

Space reactors - same principles, atoms divided , emits energy and absorb by active body,  usually liquid metal, then a difference,    instead steam turbine, a thermoelectric generator. due to not much temperature different , overall efficiency quite mediocre ... for 1000W   thermal power probably 70W electrical ....   the rest 900+ watts need to dissipate , usually by emitters, due to vacuum ...
 
technically gases can be used to spin turbines in a space,  Problem A- gas will be lost , need replenish, B- low efficiency due to gas masses,  C- heavy spinning turbine not for a long time. D - everything sealed as part A. E- deal with hot gases , that a headache, metals absorb it and changing internal structure , etc ...

if ...  thermoelectric .... then 40kW electrical transfer to 500 kW thermal ,  and rather heat the core of the moon ,  I have no clue how to dissipate it ...

I think It great, and absolutely doable project, with minimal investment (pen and paper don't cost much), with very solid result ...