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Member postings for Robert Atkinson 2

Here is a list of all the postings Robert Atkinson 2 has made in our forums. Click on a thread name to jump to the thread.

Thread: Chinese speed controller
12/06/2019 13:38:22

A 12V (or better 24V e.g. truck) brushed DC motor like a wiper motor and a PWM controller would probably be a good opton for light work on a Pultra at higher speeds. PWM controllers are available on ebay and are cheaper than variacs and inherently safer being low voltage.

12/06/2019 11:20:57

That controller is totally unsuitble for a lathe motor. It does not even have a power or current rating. They are intended to control small shaded pole induction motors of the type used in fans, maybe a few tens of watts maximum. They don't even do a good job of that. They effectively limit the power to the motor so it never gets to synchronous speed.
It almost certainly does not meet safety an interference regulations either.

The only way to properly vary the speed of an induction motor is to change the frequency of the power to the motor using a VFD or inverter. This will work on single phase motor over a limited range but it is much better to change to a 3 phase motor. If the single phase motor has a run capacitor theen this would have to be switched to different values for different speeds.

Robert G8RPI.

Thread: Electrics for a battery locomotive
10/06/2019 08:57:29

It's a really good idea to fit an isolator switch like this:

https://www.ebay.co.uk/itm/Universal-12V-Battery-Isolator-Switch-Kill-Switch-Winch-Isolator-DA2037/371193793900?epid=1326302701&hash=item566cdfcd6c:g:Z8wAAOSw0vBUbP7f&frcectupt=true
(random ebay item also available from motor factors and the like)

close to the battery.

Apart from an emergency cut out for a electrical fire or motor controller runaway they are a handy security measure. If you leave the loco for even a minute, take the key with you. You can it on an expanding key chain so you have to take it with you.

Robert G8RPI.

Thread: Electricity Supply
09/06/2019 18:09:28

A really good book on energy is "A cubic mile of oil"

https://www.amazon.co.uk/Cubic-Mile-Oil-Realities-Averting/dp/0195325540

Not cheap though

There is some free info here http://global.oup.com/us/companion.websites/9780195325546/

The short term future for cars is clearly hybrids. My peronal vuew of the ideal is an electric drive train with a high efficiency IC engine running at it's peak efficiency load point driving generator. Maybe a tiny gas turbine runnnng on LP or even better hydrogen. Generator only needs to be big enough to give range extension, around te average power used by the car.

Robert G8RPI.

09/06/2019 11:20:14

Back to the electric / IC comparison. Quick wed search gives a Nissan leaf at £318 pm and a Fiat Panda 5 door at £155 PM (including inital payment) Plus £12 pm road tax for the IC car gives a difference of £151 pm. Assumng about 40 MPG thats 0.11 litres per mile at £1.5o per litre (inflation allowance) thats 17p per mile so the Panda can do 880 miles per month (10,000 per year) for "free". Even at a typical mileage payment of 37p is 400 free miles per month (4900 per year) even if the Leaf was charged for free.

Robert G8RPI.

09/06/2019 10:37:00
Posted by not done it yet on 08/06/2019 18:16:55:
Posted by Robert Atkinson 2 on 08/06/2019 08:45:39:

This is a very valid point about plug in vehicles. Rather than looking at max power look at range and batttery capacity in kWh The new Nisan leaf is 160miles and 40kWh so thats 250Wh per mile. A 2h commute at 50MPH is 100miles and 25kWh so still over 100A. for a 10h charge.
Good excuse to get a 3 phase supply laid indevil

There is also the question of where the electricity will come from. We need more (next generation) nuclear power.

My employer also owns a car dealership and a few years ago we were offered a deal for 50% off the lease cost of a small electric car (had to participate in research study data logger etc). I did the sums and even charging for free at work it would still be cheaper to run my 6 year old 150hp turbodiesel estate car for 4 years and then scrap it than to lease the electric.

Robert G8RPI

Edited By Robert Atkinson 2 on 08/06/2019 09:09:54

Some of this post is sensible. But:

Exactly how does 25kwh,over 10 hours, equate to 100A?

By simple calculation that would be 2.5kW for ten hours (ignoring innefficiencies) 2.5kW is rather less than a 13 A plug can deliver. So let’s get real! I suggest you try again!

So no reason at all for a 3 phase supply.

More renewables is what is needed, not necessarily more nuclear. Not that any intermittent energy supply will cover all loads all of the time, of course. We need a lot more tidal generation as well - output can be calculated years in advance - and more storage (a small amount compared with hourly usage - but every bit helps. Better to import energy via inter-connectors, but that, of course, carries problems with out-sourcing a national necessary commodity.

Clearly electric car leasing has come down in cost since “several years ago”.

Your case study does not provide any detail. One cannot fairly compare a “small electric car”. For a start, the ICE car had been written down to a quite low value after 6 years, so comparing the capital value of an old car with the historical high cost of electric cars several years ago (expensive and low range). The ICEcar may well have been ready for the scrap heap after ten years, anyway ( my current ‘run-around’ is a small diesel which is about 22 years old, mind)

So only the first paragraph is sensible.

You are correct on the current, 100A is a 1 hour charge. I really must pay more attention.
There is no renewable or combination of renewables that can provide 24/7/365 supply without storage. Batteries (in "walls" or cars) are not a viable long term solution.
My car comparison was a personal situation, not generic. The diesel estate is still going strong over 4 years later. The cost of an electric would still be more than a diesel for me even for a new lease (at full price).

Robert G8RPI.

08/06/2019 15:42:47
Posted by pgk pgk on 08/06/2019 12:20:31:

My home charger runs at 32A and puts in 7+KW/H for 22miles/H range on a 100KW Tesla which is a heavy car. Their latest Model3 LR has a 75KW pack and goes over 300 miles on a full charge which you should get at home in 10hrs. Peak KW is over 250 compared to your current 80KW.
Charging from the latest generation superchargers can peak at 250KW but in reality the golden area from 20-80% will top-up in 15 mins.
As for electricity bills even without the benefit of night rates it's under 16 squid for a full charge on mine and in warm weather I can get the full 310 range so 5p/mile 'fuel' (double that cost in cold winters). The model3 being lighter and smaller pack etc is more economic.


As to supplying the countries all electric needs.. well that's got a lead time of many, many years to up our game on supply.

One of many interesting ideas is to use old EV car battery packs as home storage units and up our solar panel use.

pgk

Well your 32A may be 7.3 kW draw on the mains but it's not putting 7+kW per hour into the battery. Firstly there is the charger efficiency, maybe 95% so 6.99kW out. Battery charge efficiency is 99% at best so 6.9kW (not including any loses in cables etc). This is as you say worse in winter not least because you have to heat the battery pack. Typically you would need 14-15h for a full charge. Not often you would need a full charge.

On new nuclear, it can of course provide extra capacity, you just have to build enough.

Robert G8RPI.

08/06/2019 08:45:39

This is a very valid point about plug in vehicles. Rather than looking at max power look at range and batttery capacity in kWh The new Nisan leaf is 160miles and 40kWh so thats 250Wh per mile. A 2h commute at 50MPH is 100miles and 25kWh so still over 100A. for a 10h charge.
Good excuse to get a 3 phase supply laid indevil

There is also the question of where the electricity will come from. We need more (next generation) nuclear power.

My employer also owns a car dealership and a few years ago we were offered a deal for 50% off the lease cost of a small electric car (had to participate in research study data logger etc). I did the sums and even charging for free at work it would still be cheaper to run my 6 year old 150hp turbodiesel estate car for 4 years and then scrap it than to lease the electric.

Robert G8RPI

 

Edited By Robert Atkinson 2 on 08/06/2019 09:09:54

Thread: Tyrosemiophilia
07/06/2019 13:04:00
Posted by Bazyle on 07/06/2019 12:19:39:

Why on earth do people do it?
Anyone with other unusual collections?

Old tools do not count. That's perfectly normal.

Geiger counters, other radiation detectors and radioactive material

Robert G8RPI.

Thread: Hexagonal Socket Drive
07/06/2019 12:37:04

I wonder if it has anything to do with IP? Snap on used square but don't seem to have patented that
**LINK**

Maybe someone in the UK had a patent on square drive?

Thread: Recommendation for a 3 phase electricity book?
07/06/2019 07:17:36

What do you want to know, theory, practical uses, installation?

If searching, try polyphase rather than 3 phase

Try this for theory

https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-061-introduction-to-electric-power-systems-spring-2011/readings/MIT6_061S11_ch3.pdf

Mind you all that math does not turn the light on

https://www.youtube.com/watch?v=8ve23i5K334

Robert G8RPI

Edited By Robert Atkinson 2 on 07/06/2019 07:18:55

Edited By Robert Atkinson 2 on 07/06/2019 07:24:02

Thread: Connecting a pair of motor controllers.
06/06/2019 12:37:34

Ron said

"Using a digital tacho I found that two of the motors are quite close within 2-3% of each other with a third motor approx 4% slower and the fourth 5% faster. The slowest to fastest motor are within 9-10%, this is all with the motors unloaded of course. I am quite happy with that, the four smaller motors I have in the 0-4-0 are only good to within 10% and they have proved to be fine with no issues on the track."

An off-load test is not representative at all. The speed is dependent on the voltage (supply x %PWM) and load. With no external load the actual load on the motors is just the bearings and brushes and these are very variable between motors. This probably accounts for most of the speed difference you are seeing. When loaded the resistance of the motor and connecting wires will help share the load between the paralleled motors. To help this, make the parallel connection at the controller, not the motors. This means running two pairs of wires from the controller, one pair to each motor. Ideally the wires should be of similar length other wise the motor with the shorter wire will take more of the load.

Robert G8RPI.

05/06/2019 12:55:34

From the photo this appears to be a basic PWM controller probably a sawtooth oscillator, variable voltage (from pot)and comparator. While two could be modified to run from one pot I don't think a simple parallel connection is advised.
There are two reversing relays and depending how they are wired they probably provide dynamic braking (also using the MOSFET source drain diode and battery) when the control switch is off. A separate double pole "off" switch or a pair of microswitches operated by a cam on the throttle control would be easier than trying to find a dual gang, 100K linear pot with a double pole switch. I found a 50K, which might be OK but it's a single pole switch so needs investigation or a relay and it looks pretty poor quality.

**LINK**

A professional modular pot and switch would be expensive.

You could try hacking one of these

**LINK**
and one of these

**LINK**

together. I.e put the switch of the single onto the double.

Where are you located? Maybe someone come and have a look at the controllers.

Robert G8RPI.

Thread: A day of coincidences
04/06/2019 12:50:40

One advantage of online ordering is you can cancel it or return the item....

Thread: Connecting a pair of motor controllers.
04/06/2019 12:47:45

Another option, depending on your batteries would be to use 48V and run the motors in series/parallel on one controller. Series the two motors sharing an axle and parallel the two bogies. If you series the bogies then one slipping would "take" all the voltage and you will loose power at the other bogie.

Otherwise I concur, a dual pot is the way to go. If I had a controller to hand I'm sure a simpler control could be worked out, but I don't.

To keep it mechanical you could of course make a throttle lever and gear (ot miniature toothed belt, crank etc) to the two control pots.....

Robert G8RPI.

Thread: Quicksilver
04/06/2019 07:19:23

To answer the original question.

Yes Bob would be liable to prosecution under the explosives precursors and poisons (EPP) regulations. Max penalty is 2 years in prison.
You now need a licence to possess many previously common chemicals. If the Hg was sealed in a valve, lamp or instrument it is exempt, but a bottle of it needs a licence. Also applies to battery acid, many plating chemicals etc. Note that it does not apply to professionals or businesses.

See:

https://www.gov.uk/government/publications/licensing-for-home-users-of-explosives-precursors/licensing-for-home-users-of-poisons-and-explosive-precursors

Robert G8RPI.

I'm not a lawyer but this one is pretty straightforward. Get professional legal advice if you need it , but I doubt there is much case law on this one yet, don't be the first.

Robert.

Edited By Robert Atkinson 2 on 04/06/2019 07:19:44

Thread: Connecting a pair of motor controllers.
03/06/2019 19:07:12

Can you provide details of the controller model?
The more advanced conntrollers actually use a 0-5V (or similar) control voltage which is generated by a potentiometer a 5V supply. If thi is the case you could use a single pot with 3 connections (common, 5V and variable) to one controller and two (common and variable) to the other. If they are cheap ones using a RC circuit then you will need a dual potentiometer. Make sure that it is linear NOT log or "audio" taper. The matching between sections would normally be better than 5%.

https://uk.rs-online.com/web/p/potentiometers/1638384/

Rober G8RPI

Thread: Rejects for Sale.
01/06/2019 14:09:51

Another well documented issue is the inclusion of terminating resistors in Chinese "ELM327" OBDII car diagnostic interfaces. These are used to read fault codes etc on cars by interfacing to the CAN bus. This bus is terminated on each end by a 120 ohm resistor. As a resistor appears on the data sheet application typical circuit the Chinese include it. This results on 3 resistors connected to the bus and depending on other factors like cable length and number of bus nodes this can stop the bus working properly. Remving the resistor from tye interface fixes the problem. It's been known about for years but they keep fitting them.

Robert G8RPI.

Thread: Electronic Indexers - How Is Cumulative Error Avoided?
30/05/2019 17:47:24

While microstepping improves torque ripple and position overshoot, it does not necessarily provide improved positional accuracy. This is particuarly true ff the load (torque) is variable. Performance depends on the motor, controller and load. It's easy to get caught up in the numbers but the whole system must be considered or you may be wasting effort for no real improvement.

Robert G8RPI.

Thread: Should I have 3 phase supplied to my house?
30/05/2019 09:24:22

A proper three phase supply would be a positive advantage if you are at all likely to buy an electric or plug-in hybrid car in the future. It would allow the installation of a fast charger.
Additionally what is the rating and load on your existing single phase supply? Many only have a 60A feed which is 14kVA. This seems a lot but if you have electric heating / cooking / shower you might be running int the limits at peak demand.

Alternatively take a tap off a couple of neighbours of street lights for the other two phasesdevil
(just for clarity that;s a joke I don't advocate stealing electricity or making dangerous taps into wiring.)

Robert G8RPI.

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