tachometer wiring

[geoff adamsParticipant @geoffadams14047]

having trouble wiring this up I know nothing about electronics

this is for my boxford lathe that I,am fitting a variable speed moter

please see the info supplied

the sensor has three wires brown blue and black I assume that these connect

to the readout and the other two are the power

can I use a 12v phone charger ?

any help please Geoff

[geoff adamsParticipant @geoffadams14047]

[Clive Brown 1Participant @clivebrown1]

Sensor wires as per colour. +ve power to terminal 1. -ve power tp terminal 2. Terminal 4 not used.

'Phone charger is unlikely to give enough volts. 8+ v. is needed

The magnet needs to present the "correct" pole to the sensor, which lights up when it's working, or at least, mine does.

[geoff adamsParticipant @geoffadams14047]

thanks Clive

wired it up as per your instructions this morning now works a treat

Geoff

[JIm PowneyParticipant @jimpowney74686]

Gents

I have the same Chinese tacho with a hall sensor as the first post

We have a Large Mixer that we want to display the RPM for operatives

I Have wired as above diagram from a permanently fed 24vdc supply within the mixer and also tried the Blue sensor wire to either terminal 2 or 3 (0Vdc and Scn earth) and works the the same on both (as proposed in the below link) with Terminal 4 unused

https://www.model-engineer.co.uk/forums/postings.asp?th=112167

We have also tried teh Black sensor wire to all pins including swapping teh Black/Blue cables to see if that made any difference but seems to function

However, we get 0000 displayed on tacho and red LED on back of hall sensor – as expected with voltage applied and Shaft NOT TURNING

regardless of how we wire the combinatoin of VDC/Tacho/Sensor when we start the shaft rotation the tacho shows 4 dashes "- – – – " and does not change even though the sensor seems to react to the magnet when the shaft is NOT spining

Does this sound like a faulty Hall sensor or some kind of voltage interference from the mixer itself?

the 24vdc comes form terminals connected directly to a 24vdc rectifier which is fed from a 220/24vac transformer

Do I really need a dedicated DC Voltage supply?

Any help appreciated

Jim

[Brian Sweeting 2Participant @briansweeting2]

Posted by JIm Powney on 03/07/2018 11:01:02:

Gents

I have the same Chinese tacho with a hall sensor as the first post

We have a Large Mixer that we want to display the RPM for operatives

I Have wired as above diagram from a permanently fed 24vdc supply within the mixer and also tried the Blue sensor wire to either terminal 2 or 3 (0Vdc and Scn earth) and works the the same on both (as proposed in the below link) with Terminal 4 unused

https://www.model-engineer.co.uk/forums/postings.asp?th=112167

We have also tried teh Black sensor wire to all pins including swapping teh Black/Blue cables to see if that made any difference but seems to function

However, we get 0000 displayed on tacho and red LED on back of hall sensor – as expected with voltage applied and Shaft NOT TURNING

regardless of how we wire the combinatoin of VDC/Tacho/Sensor when we start the shaft rotation the tacho shows 4 dashes "- – – – " and does not change even though the sensor seems to react to the magnet when the shaft is NOT spining

Does this sound like a faulty Hall sensor or some kind of voltage interference from the mixer itself?

the 24vdc comes form terminals connected directly to a 24vdc rectifier which is fed from a 220/24vac transformer

Do I really need a dedicated DC Voltage supply?

Any help appreciated

Jim

Turn the magnet around, north to south poles or the other way, this caught me out when I installed mine last year.

[Harry WilkesParticipant @harrywilkes58467]

The hall sensors I have used favour the south pole

H

[SillyOldDufferModerator @sillyoldduffer]

Posted by JIm Powney on 03/07/2018 11:01:02:

…the 24vdc comes form terminals connected directly to a 24vdc rectifier which is fed from a 220/24vac transformer

Do I really need a dedicated DC Voltage supply?

…

The output from the rectifier will be pretty rough and might well explain your symptoms. Electronics vary in their ability to cope with horrible power supplies but generally they don't care much for mucky DC. The voltage may also be more than the tachometer can cope with. (24V RMS has voltage peaks nearly 3 times higher, ouch, and the poor thing might be damaged.)

I'd clean up the rectifier output with a down converter unit like this example. I'm not sure this particular unit is suitable because it also has to deal with whatever your 24V rectifier is poking out, but the type cover a wide range of conversion voltages. A different model may be more appropriate.

Otherwise a laptop PSU or wall-wart would do the job if there's room and you're confident wiring it safely to the mains.

Electrical noise from the mixer itself is a possibility, but the most likely route into the electronics is via the power supply, and a better PSU should clean it up too.

Are you able to test the setup by powering it temporarily from a battery? If it works OK off a 12v car battery or similar, it must be a power supply problem.

Dave

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