Here is a list of all the postings Ed Dinning 1 has made in our forums. Click on a thread name to jump to the thread.
|Thread: Inverter drives for single phase motors|
Hi Gents, thanks for the inputs.
The application is a forced draught fan for a wood burning boiler.
Original equipment is a 250w cap run induction motor that is working well. It originally used an Italian made inverter as a 2 speed VFD.#This has died with no obvious faults and no way to get a schematic.
The PCB logo is (RD)² . It appears to have many more facilities for control than were needed, but no details of how to activate them so we can have full speed and about 1/2 speed,
I've since found Invertek drives and their Optidrive range has a single phase in, single phase out inverter for fan and pump use that can be configured as I need it, as well as many other features that I will never use.
Anyone familiar with this unit ?
Hi Gents, has anyone recommendations to make for the use of inverters on 230v. single phase, to run an induction motor(single phase, cap run, 230v); or have they successfully used them ?
Maker, supplier, likely price ?
A simple unit is all that is requires as the motor drives a fan and only 2 speeds are needed. One near max and the other about 1/2 speed.
Many thanks, Ed
|Thread: 24v dc motor powering a drill press|
Hi Steve, if you can get the electronic controller that went with this motor, many of your problems will be solved as it will give variable speed with a current limiting characteristic, so speed should not drop with load.
You will then need a fairly hefty mains to 24v DCpower supply unit.
|Thread: Low rate automatic house plant watering system|
Hi, opaque or black plastic watering pipes will stop anything growing in the low water flows and the heat.
A header tank or resevoir and then a peristaltic pump for low flow rates, through chokes if necessary to equalise flows.
|Thread: 540 Motor as a generator|
Hi Gents, I misread the original posting, possibly best way to proceed is to run the motor at about the proposed speed and see the output voltage. Depending on type LEDs often need about 1.5v per device. It should then be possible to see how many you can fit in a string. Several parallel strings could then be operated as they typically need about 10mA or so peer string.
Hi Robert, a boost mode regulator would work, but tends to be configured to supply a constant output voltage.
I believe that this unit is to be used as a tacho generator and drive a voltmeter calibrated in RPM.
If you look at op amp (operational amplifier) circuits, (the 741 is a typical device) it can be configured with 2 resistors to have a gain of 10, 20 etc. The output of the op amp then feeds a voltmeter calibrated in RPM.
With most modern voltmeters or "meter LCD modules" the load taken is small so little power is used.
These motors would be a pain to rewind for more volts out. The simplest way would be to use a simple op-amp circuit to boost the voltage driving you meter. This would also have the advantage of reducing the load on the motor (generator).
|Thread: Arc welder cooling oil.|
Hi Jonathan, exactly my thoughts, but no sign of one on mine. I have some cork, so I'll add it to the jobs list.
Hi Gents, I also have a "steel tank on wheels" arc welder. It is a good piece of equipment, but if "heaved about" will slop oil from under the top cover. It has a breather on the top, but no apparent gasket between the top and sides.
Should one be fitted here?
Hi Gents, as far as I know, PCB containing oils were only used on larger distribution / HV transformers due to cost.
It also has a higher gelling point, so is quite viscous at low temperatures.
You could also be offered switch oil, a similar compound but with some detergent action to remove the arc products from switch operation. This should also be suitable for a welding transformer.
|Thread: Tool/cutter grinder using Lidl grinder disc|
Hi Gents, many thanks for the information, article now found.
This thread can now be closed
Hi Folks, now that Lidl have their excellent angle grinder diamond impregnated discs back in stock, I thought I would make myself a cutter grinder similar to the one that appeared in MEW some time ago.
Despite searching the indexes I cannot find a reference to this article; could some kind reader point me in the right direction (It was not the Marl Noel article in 242), and save me having to go through a large pile of magazines.
Many thanks, Ed
|Thread: TDA2030A Audio Amp|
Hi Gents, 807's have been popular as amp valves for a long time now. Geloso made many commercial amps on this basis.
Due to the increasing prices for the popular (EL34. KT66 etc) valves, TV line output and similar types are now being designed in. These are valves designed for pulse operation so do not have such a linear response for Vg to Ia.
A circuit technique has evolved for this. The signal is now DC coupled into G2 (quite high level and low impedance) which has a nice linear characteristic. G1 is used to set the bias level on the valve as normal.
Hi Gents, split bobbin transformers tick all the boxes for the H&S brigade in terms of leakage pri/sec etc BUT, they have much worse regulation and higher losses, which could, with a poorly designed power supply increase distortion.
A correctly designed "sec over pri" transformer (earth screen and correct creepage and clearances) will give much better performance, use less total power and still be safe.
Note that the split bobbin design is virtually never used for the "holy grail" ~ output transformers.
|Thread: Absorption fridge tech details|
Hi Gents, thanks for the details so far.
Unfortunately I am fixed on the 12v supply route, so any further tips or details of the thermodynamics of the system would be much appreciated.
Hi gents, thanks for the ideas so far. This project can only use the 12v heater, but what happens if I vary the supply to the heater, or changes its position in the pipework with that of the 240v one?
Hi Folks, I'm working on optimising the "Electrolux type" (actually Dometic) caravan multi fuel fridge I have to operate on 12v DC. This is actually the poorest "fuel" in terms of cooling performance.
I'm looking for any books or articles on the design of these units, especially the positioning of the various heaters and details of power in to cooling delivered.
Many thanks, Ed
|Thread: recent joiner, but old engineer|
John, yes should see you in April
Howard, there are quite a few ME clubs in the Newcastle area and I also have my own workshops for metal, wood and electronics. One of my main activities, with a group of similar retired professional engineers, is Rriends of Discovery Museum.
Main activities are repairs and refurbishments to various exhibits and displays as well as applying for grants for new exhibits, talking to visitors and bringing old exhibits back to display.
If anyone is interested in joining us please come along to the museum any Tuesday morning and find out what we do.
Highlight of this year will be the arrival of Stephenson's "Rocket" from the science museum for display for the Great Exhibition of the North, from June to Sept.
|Thread: Myford chuck 'oiling point'|
Hi Gents, should have made it clearer, PTFE spray works best is chuck is stripped, but works pretty well if the jaws are simply wound out to expose the scroll.
Hi Gents, I have with success used PTFE spray as it is non sticky so no swarf pick up and it leaves a very fine film.
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