By continuing to use this site, you agree to our use of cookies. Find out more

Member postings for Les Jones 1

Here is a list of all the postings Les Jones 1 has made in our forums. Click on a thread name to jump to the thread.

Thread: Blown band saw circuit.
31/08/2020 20:49:17

Hi Marsh,
It looks like the "1" reading is your meters way of indicating over range. (Open circuit.) I now have confidence in the resistance readings in your last post. They seem to indicate that the schematic I drew is wrong. If it was correct then without the solenoid pressed in 4 to 8 should be open circuit (Your meter reading "1".) and with the solenoid pressed in it should have read 0 ohms.Can you confirm that it was the overload trip button that you had to hold pressed to get the motor to run after the initial fault ? (NOT the start button as originally thought.) Have you checked that the motor is free to turn by hand ? What is the mains voltage in your country ? (I am thinking that if it is 110 volts Then a overload trip for the 240 volt version may have been supplied. This would be about half the current rating required for the one for 110 volts. You do not need to worry about about the capacitor. It is wired the same way as it would have been wired if it was strapped to the motor. The NVR switch I linhed to is a 240 volt version but you may need a 110 volt version.

Les.

30/08/2020 19:52:14

I have just been reading through the thread again. I had misread the first post and thought that the motor ran when the start button was held pressed but you actually said when the TRIP SWITCH was held pressed. All I have said so far is not relevant. If you have to keep the trip switch pressed in then the motor is taking too much current or you have been supplied with the wrong current rating of trip switch. (You should never hold a trip switch in as it is designed to remove the supply id the load is taking too much current.) Sorry for my error in reading your first post.

Les.

29/08/2020 18:11:07

Hi Phil,
I agree that it looks like the spring clip holds the contact assembly to the solenoid part. I did think about suggesting trying to remove the contact assembly but decided that springs and other bits might fall out. I have just seen Emgee's post (I opened another session to look at the NVR pictures again to avoid loosing what I had typed.) I agree that my schematic may not be correct. This is my reasoning. What I assume to be contacts 3 to 7 and 4 to 8 seem sensible to provide double pole switching to the motor. As the indicator light is connected to 1 and 5 it seems likely that the coil is connected between those two points. This left 2 and 6 which seem to be wired as the maintainer contact. I am trying to understand Marischal's readings. In his post at 11:12 on the 26th he says the reading between 1 and 5 is "thing" and the reading between 2 and 6 is "nothing". I assumed by nothing he meant open circuit but he has not yet told me what he means bu "thing". In his post at 18:22 on the 26th he says the meter stayed at "1" I initially thought he had a reading of 1 ohm (Or 1K or 1M) but I am now wondering if just 1 (As opposed to 1.00) could mean overrange on his meter. I am waiting for clarification on this.

Les.

Edited By Les Jones 1 on 29/08/2020 18:11:45

27/08/2020 18:54:20

Hi Phil, Many of these NVR switches do not even have a separate maintainer contact. If It turns out that the only fault is the maintainer contact (2 to 6) then I am going to suggest linking 1 to 4. I think it is unlikely that the 2 to 6 contact AND the coil have both failed.

Les.

27/08/2020 14:58:16

I am even more confused. Are you using an analogue or a digital meter and if it is digital is it auto ranging on the resistance setting ? I don't understand the 1 reading. (You don't say if this is 1 ohm, 1 K ohm or 1 Meg ohm.) Normally on a resistance range with the test probes not conneted to anything or each other the meter would display something like ol to indicate the resistance between the probes is higher than the meter is capable of reading. If the probes are shorted together it would read 0.00. (If it is set to al low resistance range it can give a small reading of probably les than 1 ohm which will be the resistance of the test leads.) Does your meter behave this way ?

Note to Phil. This type of NVR switch does not have a normal start an stop button. The start button just manually pushes the solenoid to the closed position and the stop button just forces the solenoid to the open position.

Les.

Edited By Les Jones 1 on 27/08/2020 15:00:05

26/08/2020 17:42:13

I assume that when you say "nothing" you mean infinite resistance. If not what do you mean ?

What was the resistance reading between 1 and 5 ? (I don't understand what you mean by "thing".)

Les.

Edited By Les Jones 1 on 26/08/2020 17:43:33

26/08/2020 08:37:54

If the fault is the contact set 2 to 6 then it should be possible to get it to work by a small change to the way it is wired.

Les.

25/08/2020 20:54:57

This is my interpretation of the wiring.

band saw.jpg

Contacts 3 to 7 and 4 to 8 must be working as the motor runs while the start button is held in, (The start button just pushes the solenoid in,)
The fault must be the coil is open circuit or contact set 2 to 6 not closing. With the mains cable unplugged first measure the resistance between 1 1 and 5. You should get a reading of a few hundred ohms. Then connect your meter to 2 and 6, You should get a very high (Probably over range reading.) Then push the solenoid armature in. The reading should drop to close to zero ohms. Report the result of these tests.

Les.

23/08/2020 18:14:00

There is probably a centrifugal switch inside the motor that disconnects the start winding when the motor is up to speed. Probably an NVR switch such as this can be used. (There are also many advertised on ebay.)

Les.

23/08/2020 17:35:43

It sounds like either the coil on the coil on the contactor is open circuit or the maintainer contact is not holding the coil in after the start button has been pressed. The stop button will be a normally close push button and if that was open circuit it would also prevent the the coil from holding the contactor in. I assume the rectangular thing with 8 connections is the combined contactor and start and stop buttons. you have not shown which connections go to the coil or the layout of the contact sets. I have tried to find a picture of your contactor assembly but failed. Some pictures of the contactor may help in understanding the contact and coil connections. I think a standard NVR switch can be made to work.

Les.

Thread: Coping with voltage spikes
13/08/2020 20:04:52

Tim, You are going to have to provide more information on the "LED". A single actual LED (I am assuming it is a white LED as different coloured LEDs have different forward voltages.) would have a voltage of between 3.0 and 3.6 volts across it when driven with it's rated current. As you are calling it a 12 volt LED it must contain something to limit the current and it may consist of more than one actual LED. Until we know more about the "LED" we can't work out a possible reason for it failing.

Les.

Thread: Death of a PSU
25/07/2020 11:52:20

The TNY264 is also a 7 pin low power switch mode regulator chip. It would be nice to know the part number of the chip on the board as the picture is not good enough to read it.

Les.

Thread: Son`s mini lathe Clarke CL300
17/07/2020 09:23:14

This is a link to the manual for the CL300M which contains a wiring diagram but not a schematic of the board. (Which I have not been able to find.)

Les.

16/07/2020 20:24:32

Am I correct that when you say " mixed up he has said they were the ones going to the emergency stop button the on and off." that you mean that he connected the output of the on/off switch to terminals K3 and K4 and that he connected the wires from the emergency stop switch to terminals L1 and L2. If so I don't see that this would cause the varistor to fail but it almost certainly would have damaged other components as he connected the mains to the low voltage part of the board. The varistor is probably connected directly across the mains input to the board (terminals L1 and L2) so I think this just failed or failed due to a high voltage transient on the mains.

Les.

15/07/2020 22:17:50

Telling us which wires you connected to the wrong place may help to identify what damage you have done. Tell us the correct places the wires should connect to and where you actually connected them. can you also post a picture of the under side of the board near the burned area.

Les.

Thread: Voltage feeding DRO "usb" digital scales?
02/07/2020 09:01:56

Hi Robin,
I started using Chinese scales with the Shumatech DRO350 many years ago. There was a lot of discussion on the Shumatech forum about jitter on the displayed values when the scales were supplied from the DRO 350 rather than their internal button cell. A few of us traced this to the fact that there was a section of PCB track between the 1.5 volt regulator and the negative connection to the scales that also carried the negative supply to the multiplexed LED display. The multiplexing current caused a small amount of voltage ripple along this section of track which was enough to cause the readings from the scale to jitter. This showed that the scale reading was effected by variations in the 1.5 volt supply. So I think adding the regulator reduced the sensitivity to battery voltage variations. Also using the CR2032 increased the battery life.

Les.

01/07/2020 20:28:00

Hi Robin,
I have some digital calipers that use CR2032 cells but the data output is still 1.5 volts. I think they have a built in regulator to drop the 3 volts down to 1.5 volts.

Les.

01/07/2020 09:09:39

I have always supplied this type of scale with 1.5 volts when using home made remote displays. I think you will find the remote power connections connect directly to the internal battery contacts. The recommended silver oxide cells are rated at 1.55 volts when new. I have used an LM317L to provide the 1.5 volts supply from the 5 volt rail for the logic in my remote displays. Although USB connectors are used on these scales they DO NOT use USB protocol.

Les.

Edited By Les Jones 1 on 01/07/2020 09:10:19

Edited By Les Jones 1 on 01/07/2020 09:25:05

Thread: 3 Phase in a Model Engineers workshop
18/06/2020 16:48:20

Hi Tony,
Good look with finding someone local that can help you. I'm Sure we would all be interested in knowing the the solution to the problem. (And giving any more assistance if required.)

Les.

17/06/2020 14:35:18

Hi Phil,
At first I had doubts about it being a ROTARY converter as I could net see the motor part of the converter. At sight it looked like the converter box was right against the wall. On the Transwave website the motors all seem to be mounted on the back of the box. I had a closer look at the picture and I think I can just see the fan end of the motor behind the output socket. I can't understand how the contactor can pull in when fed via the start button but not by the maintainer contact. The only thing I can think of that may be happening is the contactor is chattering in and out while the start button is pressed. When it pulls in and the load is put on the phase that is supplying the coil the coil then drops out. As soon as this happens the load on the phase that is supplying the coil is removed so it pulls in again. If this is happening then it would not hold in when the start button is released. Monitoring the coil voltage (Or listening for noise from the contactor.) would prove or disprove the theory. (I am assuming that there is no fault in the internal machine wiring as we where told is was working in the previous location.)

Les.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
ChesterUK
emcomachinetools
Warco
Eccentric July 5 2018
JD Metals
cowells
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest