Test Equipment Anonymous (TEA) group therapy thread

[Robert763]

Today I received a package which contained, along with some MS contact insertion/extraction tools, a really strange tool. It is a folding switchblade saw-cum-screwdriver, with a neon test lamp in the handle connected to the blade.
The blade has switchblade action to open and locks in the open position. The saw is not really very sharp and there is a cable-stripping groove too.
I feel a bit like watching a cow electricians' version of Gary Larsons' 'Cow Tools' cartoon.
WTF?
Mooooo!

Carry that in public in the UK and you could be locked up if the police find it.  don't even go there.

[bd139]

Depends where you get found with it and intent. You’re probably ok if you’re not wearing a good in McDonald’s car park.

Well scope bouncing ball thing is working in default configuration. Building 3 more of them to check component tolerance issues next. Looking for better opamps for low voltages as well.

[Robert763]

Gah on that I was just watching this 

This guy is the FPV equivalent of ElectroBoom; a complete fucking moron. You don't run any modern BL motor without a prop; they're too high performance. The ESC loses necessary commutation feedback and goes out of sync, and then you wind up with a LO side FET still biased on when the next commutation fires the HI side, and POOF! Dead short through the windings and fire. If not, then the bell grenades as the magnets are only held in place with machined slots & epoxy.

I wish I had that kind of money to waste making myself look like an idiot. 

mnem
 

Apart from the obvious idiocy here, the failure is not electrical. The lack of a load has no effect on the speed of a BLDC, jut the current. A BLDC is not a  I don't think overheating or bad commutaion was the cause of the failure either.
The aluminium rotor bell failed under the G force / fatigue. This resulted in los of the magnets. No electrical failure so far. The loss of the magnets significantly reduces the back EMF which is the main thing limiting the current. Current shoots up and windings fail through I2R heaing.
They are lucky a magnet did not hit someone.

[Robert763]

Depends where you get found with it and intent. You’re probably ok if you’re not wearing a good in McDonald’s car park.

Well scope bouncing ball thing is working in default configuration. Building 3 more of them to check component tolerance issues next. Looking for better opamps for low voltages as well.

No intent required for a switch blade or flick knife, they are illegal to posses in the UK full stop. If you are lucky and pass the attutude test you might get a warning, more likely a a cautio which results in  crimnal record.
for kinves over 3" or locking knives YOU have to show a good reason for carrying it in a public place, the police CPS do not have to show intent. To be on the (legal) safe side I've removed the blade locks from my regular carry Leatherman Wave. To have a knife you can open single handed and has a locking blade in public is asking for trouble. Many police forces are having crack downs on knife crime, and rightly so, but some are not adverse to making an example of an otherwise law abiding citizen a it will likely get more publicity than a regular scroat getting a slap on the wrist.

[BU508A]

Depends where you get found with it and intent. You’re probably ok if you’re not wearing a good in McDonald’s car park.

Well scope bouncing ball thing is working in default configuration. Building 3 more of them to check component tolerance issues next. Looking for better opamps for low voltages as well.

I have here a huge amount of UA709 in MIL-Spec config. Would these work your design?
They had come in a Konvolut omnibus volume of electronic parts from Rohde & Schwarz and are marked with a red dot.

Example picture (not mine):


Datasheet available here

[bd139]

Depends where you get found with it and intent. You’re probably ok if you’re not wearing a good in McDonald’s car park.

Well scope bouncing ball thing is working in default configuration. Building 3 more of them to check component tolerance issues next. Looking for better opamps for low voltages as well.

No intent required for a switch blade or flick knife, they are illegal to posses in the UK full stop. If you are lucky and pass the attutude test you might get a warning, more likely a a cautio which results in  crimnal record.
for kinves over 4" or locking knives YOU have to show a good reason for carrying it in a public place, the police CPS do not have to show intent. To be on the (legal) safe side I've removed the blade locks from my regular carry Leatherman Wave. To have a knife you can open single handed and has a locking blade in public is asking for trouble. Many police forces are having crack downs on knife crime, and rightly so, but some are not adverse to making an example of an otherwise law abiding citizen a it will likely get more publicity than a regular scroat getting a slap on the wrist.

It’s a not more nuanced than that ie you can own a flick knife just not carry it unless transporting. I have my grandfather’s one

Good reason is “for the purposes of work or leisure” which is usually when I carry a knife. Not down to Asda to stab up due to da beef ting fam.

[bd139]

Depends where you get found with it and intent. You’re probably ok if you’re not wearing a good in McDonald’s car park.

Well scope bouncing ball thing is working in default configuration. Building 3 more of them to check component tolerance issues next. Looking for better opamps for low voltages as well.

I have here a huge amount of UA709 in MIL-Spec config. Would these work your design?
They had come in a Konvolut of electronic parts from Rohde & Schwarz and are marked with a red dot.

Example picture (not mine):


Datasheet available here

Interesting but im trying to push this down to 5v rail to rail I think. Common mode range on them is still well away from the rails. Version 2 of the board I am working on will be designed to run off 5v with rail splitter and/or +/-15v or +/-9v.

[Zucca]

for kinves over 4"

When I was young I heard the 4 fingers width rule, I mean if the knife lenght is > 4 x fingers width then no bueno.
The reason was it could reach the heart 

[bd139]

B&Q do a nice line of screwdrivers which will come out of the other side of your victim 

[med6753]

I turned the fan around on the shaft. It is definitely "pulling" now rather than "pushing".  Not much change in noise level. Still pretty annoying. 

In other words....if the filter were installed the fan is pulling the air through it as it should. Verified with smoke from a candle. 

Edit, and the heat is now going out the top vents of the scope.

Ummm... okay... flipping the fan BLADE around will not reverse direction of airflow. ONLY changing the direction of rotation will do that. With flipping the fan blade, one way it moves lots of air, the other way not as much and usually noisier as it is just freewheeling instead of getting a proper bite in the air.

Please just humor me... post a pic of the fan as it is assembled now.

It's not like I don't know a thing or three aboot fans... I build and pilot little whirry flying things that are essentially 4 of them in CW & CCW pairs. FOR FUN. 

mnem
 

I'll post it tomorrow. Don't feel like ripping it apart right now.

As requested. Here is it how it currently sits. I flipped the fan around yesterday and it appears to now draw air in. The motor is spinning in a clockwise direction. I won't make any other changes until I hear from you. And note, if you want me to change motor direction by "flipping the bearings" you are going to have to explain in detail how to do it because I have no clue as to what you are talking about.

[mansaxel]

I always carry a Leatherman Charge Ti and a Led Lenser. Sort of spillover from when I had dreams of jetsetting around the world mixing large artists' arena gigs. (which did not happen, BTW) It's, apart from having to check bags while flying of course, gotten me into trouble exactly once -- a bouncer at a Vendor C -financed christmas luncheon (literally a swedish smörgåsbord with some season-themed specials thrown in) took notice that I (who was coming directly off work and had IMHO reasonable motivation to carry such tooling) was a potential danger. Just a very-small-empire-emperor seeking conflict in order to assert his power.  I'll never go back to that restaurant again. The christmas lunch was mediocre and something I would never have paid for myself, so no loss there.

Edit: If I'm going out to a restaurant where there's going to be a bottle of wine or similar and am not coming directly from work, I of course leave such things at home.

[bd139]

Ironically the bottle of wine on the table is potentially a more devastating weapon.

[med6753]

I always carry my Leatherman Micra with me except when I'm flying and then I have to leave it home. It would have to go into "checked" luggage and I never have any. 

[Robert763]

Gah on that I was just watching this 

<SNIP>

This guy is the FPV equivalent of ElectroBoom; a complete fucking moron. You don't run any modern BL motor without a prop; they're too high performance. The ESC loses necessary commutation feedback and goes out of sync, and then you wind up with a LO side FET still biased on when the next commutation fires the HI side, and POOF! Dead short through the windings and fire. If not, then the bell grenades as the magnets are only held in place with machined slots & epoxy.

I wish I had that kind of money to waste making myself look like an idiot. 

mnem
 

I was going to say that I didn't think he had any blade on that motor, so apart from the loading aspect on the rotor, there was also zero cooling effect on the motor either.

If you have a series wound motor and you run the motor with no form of mechanical loading then as long as the power is applied to the motor it will keep accelerating until the motor suffers serious mechanical damage or even total destruction, much same as a runaway diesel engine, very frightening thing to be around.   

<SNIP>

It's not true that a series wound motor will accelerate to destruction with no load. They will all accelerate until the back EMF generated by the rotation equals the apparent applied voltage (actual applied voltage minus voltage drop across winding and brush resistance). The problem is that this speed may be higher than the mechanical speed limit. In this case the motor may be damaged. Loading the motor increases the resistive voltage drop, reduces the apparnet voltage and thus the speed at which the back EMF equals the apparent voltage. Many conventional car starter motor fall into this category. However if you run them at lower voltage they will stabilse at a safe speed.
For a DC motor speed is proportional to apparent voltage and torque is proportional to current. Note the "apparent" voltage condition, i the motor has zero resistance this is the applied voltage but most of us don't have access to superconducting motors. It is the voltage drop across the intternal resistance that causes a DC motors speed to drop with load. If you put a posive feed pack loop in the supply to compensate for the resistive voltage drop the motor speed will remain constant regardless of load variation. I've designed systems that do exactly this. 

[Specmaster]

@med6753 ok, when you say the motto motor is spinning clockwise, from end of the motor are you observing that from, looking at the blade through the grill, or looking at the blade from the back of the motor, ie. from inside the enclosure?

[Robert763]

Depends where you get found with it and intent. You’re probably ok if you’re not wearing a good in McDonald’s car park.

Well scope bouncing ball thing is working in default configuration. Building 3 more of them to check component tolerance issues next. Looking for better opamps for low voltages as well.

No intent required for a switch blade or flick knife, they are illegal to posses in the UK full stop. If you are lucky and pass the attutude test you might get a warning, more likely a a cautio which results in  crimnal record.
for kinves over 4" or locking knives YOU have to show a good reason for carrying it in a public place, the police CPS do not have to show intent. To be on the (legal) safe side I've removed the blade locks from my regular carry Leatherman Wave. To have a knife you can open single handed and has a locking blade in public is asking for trouble. Many police forces are having crack downs on knife crime, and rightly so, but some are not adverse to making an example of an otherwise law abiding citizen a it will likely get more publicity than a regular scroat getting a slap on the wrist.

It’s a not more nuanced than that ie you can own a flick knife just not carry it unless transporting. I have my grandfather’s one

Good reason is “for the purposes of work or leisure” which is usually when I carry a knife. Not down to Asda to stab up due to da beef ting fam.

To be clear the law says
"It is illegal to bring into the UK, sell, hire, lend or give anyone the following:

    butterfly knives (also known as ‘balisongs’) - a blade hidden inside a handle that splits in the middle
    disguised knives - a blade or sharp point hidden inside what looks like everyday objects such as a buckle, phone, brush or lipstick
    flick knives (also known as ‘switchblades’ or ‘automatic knives’) - a blade hidden inside a handle which shoots out when a button is pressed ......"
(the list is longer )
so you could own one if you built it yourself, but not one given to you or otherwise aquired. For your "grandfathers" you would have to convince a court that it was given to you BEFORE the law was in place.
As for good reason, tht is for the court to decide.
Personally I don't consider it worth the risk.
Notte I had a type in my firat post, now corrected, you need good reason to carry any kinfe or laded weapon over 3" long this includes things like screwdrivers.

Reference: https://www.gov.uk/buying-carrying-knives

[Robert763]

I always carry my Leatherman Micra with me except when I'm flying and then I have to leave it home. It would have to go into "checked" luggage and I never have any.

When flying I put my Micra and Charge TI in the checked baggage and carry a Style PS on my keyring. The Style PS is approved to carry on aircraft, but final decision is with the screener so there is still a risk of loosing it.

Pre 2001 I used my Leatherman to disconnect the battery in a taxi from the airport when an electrical fire started on the M25. Swtching off did nott stop the fire.

[Robert763]

I turned the fan around on the shaft. It is definitely "pulling" now rather than "pushing".  Not much change in noise level. Still pretty annoying. 

In other words....if the filter were installed the fan is pulling the air through it as it should. Verified with smoke from a candle. 

Edit, and the heat is now going out the top vents of the scope.

Ummm... okay... flipping the fan BLADE around will not reverse direction of airflow. ONLY changing the direction of rotation will do that. With flipping the fan blade, one way it moves lots of air, the other way not as much and usually noisier as it is just freewheeling instead of getting a proper bite in the air.

Please just humor me... post a pic of the fan as it is assembled now.

It's not like I don't know a thing or three aboot fans... I build and pilot little whirry flying things that are essentially 4 of them in CW & CCW pairs. FOR FUN. 

mnem
 

I'll post it tomorrow. Don't feel like ripping it apart right now.

As requested. Here is it how it currently sits. I flipped the fan around yesterday and it appears to now draw air in. The motor is spinning in a clockwise direction. I won't make any other changes until I hear from you. And note, if you want me to change motor direction by "flipping the bearings" you are going to have to explain in detail how to do it because I have no clue as to what you are talking about.

To reverse  the motor you don't flip the bearings. You flip the stator. Take the rear bearing mount off, slide the stator off, flip the stator about its vertical axis so the lamination that was facing away from from the fan is now facing it. Put rear bearing mount back on.
This works bcause the shaded pole of the stator is nowon the other side of the rotor axis.

[bd139]

I guess I'm just going to have to beat people to death with a dildo then

Regarding the knife I possess it is completely legal to own (but not carry) as it was given to me formally in his will and he received it prior to PCA 1953 being introduced. There is still arguments over the compensation payable under OWA 2019 for surrendering it. There's also precedent set as the exact same knife is presented in the Science Museum which has not been surrendered. It's also worth a few quid and no I wouldn't sell it or take compensation for surrendering it.

[BU508A]

This may come as a dumb question, but isn't there any documentation available which is describing the function of this gear?
Including how the air should flow?   

[tonyalbus]

This may come as a dumb question, but isn't there any documentation available which is describing the function of this gear?
Including how the air should flow?   

To me a simple rule...HOT air goes up...
the fan is below.... the fan should be pushing not to pull against the natural flow

[VK5RC]

Rather bizarrely in sth aus knife carrying is ok if part of 'traditional costume' - all you have to do is to wear a kilt and you can carry a hidden knife 'skean dhu' or dark knife, typically tucked into your sock.

Here we have some ex-sudanese lads who have had some real fighting experience - their favourite weapon is a thin steak knife - it goes in between the ribbs better than a deeper blade. 😬 (makes chicken noises and backs away)

[med6753]

@med6753 ok, when you say the motto is spinning clockwise, from end of the motor are you observing that from, looking at the blade through the grill, or looking at the blade from the back of the motor, ie. from inside the enclosure?

From the same view as taken with the camera. That is from inside the enclosure.

[med6753]

This may come as a dumb question, but isn't there any documentation available which is describing the function of this gear?
Including how the air should flow?   

Not a dumb question. A quick googlefu found nada.

[med6753]

I turned the fan around on the shaft. It is definitely "pulling" now rather than "pushing".  Not much change in noise level. Still pretty annoying. 

In other words....if the filter were installed the fan is pulling the air through it as it should. Verified with smoke from a candle. 

Edit, and the heat is now going out the top vents of the scope.

Ummm... okay... flipping the fan BLADE around will not reverse direction of airflow. ONLY changing the direction of rotation will do that. With flipping the fan blade, one way it moves lots of air, the other way not as much and usually noisier as it is just freewheeling instead of getting a proper bite in the air.

Please just humor me... post a pic of the fan as it is assembled now.

It's not like I don't know a thing or three aboot fans... I build and pilot little whirry flying things that are essentially 4 of them in CW & CCW pairs. FOR FUN. 

mnem
 

I'll post it tomorrow. Don't feel like ripping it apart right now.

As requested. Here is it how it currently sits. I flipped the fan around yesterday and it appears to now draw air in. The motor is spinning in a clockwise direction. I won't make any other changes until I hear from you. And note, if you want me to change motor direction by "flipping the bearings" you are going to have to explain in detail how to do it because I have no clue as to what you are talking about.

To reverse  the motor you don't flip the bearings. You flip the stator. Take the rear bearing mount off, slide the stator off, flip the stator about its vertical axis so the lamination that was facing away from from the fan is now facing it. Put rear bearing mount back on.
This works bcause the shaded pole of the stator is nowon the other side of the rotor axis.

OK, got it. And that means I will have to splice wire to the motor leads to be able to reach the terminal strip.....correct?