Tachometers with hall proximity sensor question

B2 said:
Hi @Suzuki4evr

I think your objective for now is to simply determine if either the sensor or the digital display is burned out.

I do not think you have enough current out of the VFD 10 volt supply to use it. Also, it is not a good idea as you want it to be stable for the VFD speed input. I looked up the manual and is says 20mA and this is to power your VFD speed pot. Follow Mark's suggestion of using a 9V alkaline battery to power the sensor. Clip leads are nice to have, but if you do not have them or a battery holder you can sometimes just solder a wire to the terminals. It will have plenty of current to last for a while. Duracell 9volt batteries can put out as much as 1 Amp for a little while, but will get hot and the terminal voltage will drop down to about 7 Volts. I tested this on camera flash chargers and they would do this for 20-30 seconds before the flash was completely charged. I could charge the thing 30-40 times before the battery was low. So a fresh 9V battery will be plenty for your tests.

The VFD manual says there is an extra 200mA from the 24V supply for external use. Maybe? But be careful here. My Hitachi VFD manual implies that if you short out its 24 volt supply it is all over. I say implies, because there is only one place in the >600 page manual that it says anything about the current limit so I contacted the service center and did not get a straight answer... "Ohhhh don't do that" was the response.

Also, the 1K pull up resistor could be hooked up to the 10V supply but that might even be too much. Be careful hooking up to 24 volts even with the 1K resistor inserted. It is near the limit of where some of these electronics want to work and the digital display input may not like it. Don't know what the display wants to see, but it is probably set up for 5 volt logic sorts of levels. If you really want to try the pull up resistor, then make it larger so as to limit the current. Even a 10K or a 20K should be providing sufficent current.

These things are cheap and some times just die. Other times you may have zapped them and did not know you did so. I had one display that worked fine for about 3 days. Then just quit. Not all that uncommon. Cheap, mass produced stuff is not necessarily bad but it may not have been tested well. QC is an issue. Even many of the ones sold by big named US companies are commonly the same ones being sold in China, or at least were made in China. Where is your iphone made? Not in the USA. Is extensive QC testing required by the US company?
Click to expand...
Here is my vfd manual if you are interested to look through it. Is this the manual you already looked at?

VARISPEED Alpha Drive - Micro user manual.pdf
 
I previously reviewed the VFD manual and mentioned that the 10V output will not work. Try the 9V battery.

Spider material for a 1440GT. DOM Steel Pipe 3" OD, 2" ID, probably worth getting 12", but sold in 1" increments. I would extend the spider so it has maximum support over the spindle that sticks out and embed the magnets into the metal, I have done dozens this way and have not had any issues. You will probably need to enlarge the belt cover hole. As far as speed/RPM I do not see the need for RPM's below 100 unless you are turning a very large diameter work.

www.hobby-machinist.com

The Pm-1440gt Has Landed

Wow, looks great!
www.hobby-machinist.com www.hobby-machinist.com

Speedy Metals 3" OD x 2.000" ID x .500" Wall Other Steel Round Tube

Buy Other Steel Round Tube from Speedy Metals, America's favorite online metal store with unsurpassed service, highest quality and best selection.
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mksj said:
I previously reviewed the VFD manual and mentioned that the 10V output will not work. Try the 9V battery.

Spider material for a 1440GT. DOM Steel Pipe 3" OD, 2" ID, probably worth getting 12", but sold in 1" increments. I would extend the spider so it has maximum support over the spindle that sticks out and embed the magnets into the metal, I have done dozens this way and have not had any issues. You will probably need to enlarge the belt cover hole. As far as speed/RPM I do not see the need for RPM's below 100 unless you are turning a very large diameter work.

www.hobby-machinist.com

The Pm-1440gt Has Landed

Wow, looks great!
www.hobby-machinist.com www.hobby-machinist.com

Speedy Metals 3" OD x 2.000" ID x .500" Wall Other Steel Round Tube

Buy Other Steel Round Tube from Speedy Metals, America's favorite online metal store with unsurpassed service, highest quality and best selection.
www.speedymetals.com
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Thanks @mksj,

I will check out DOM Steel Pipe. I know the RPM is over kill. Since I had all the extra display digits I just put the magnets in. I do run my lathe at extremely low RPM sometimes, but not for large heavy work. I tend to mostly build small things. Sometimes very small things. I wind magnetic coils on strange shaped mandrels sometimes. I also intend to possibly swap out the RPM meter for a counter so that I can count turns and partial turns. I have a six digit counter on order. If I can get it to work I will put it in to the panel and add a few electronics and a switch or two so that I can run it either in the counting mode or as an RPM measurement. No real documentation on the counter so whether I can get this to work in the limited space I have is TBD.

At one point you suggested that I post my VFD conversion. I finally did so today. If you are still interested you can find it at a new thread I started:

VFD conversion via solid state electronic components. PM1440GT, VFD, 3-phase
www.hobby-machinist.com

VFD conversion via solid state electronic components. PM1440GT, VFD, 3-phase

VFD conversion using solid state electronic components. I finally finished documenting my PM1440GT lathe VFD conversion and want share it. It took me longer to write this up than it did to actually build the new electronics! (Are these sorts of things every really finished?) I apologize...
www.hobby-machinist.com www.hobby-machinist.com

Dave
 
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Suzuki4evr said:
Here is my vfd manual if you are interested to look through it. Is this the manual you already looked at?

VARISPEED Alpha Drive - Micro user manual.pdf
Click to expand...
Yes, I found the manual by looking at the picture of it you posted and then searching the web. alpha-drive-micro-manual.pdf is what I downloaded off of the web. page 22 yielded the current values for the 10V and 20V outputs. You are not suppose to use the 10 volt supply for anything other than the frequency setting pot. If you were to connect it to other things that might inject noise on to the pot that might be bad. They tell you 20mA so that you will know what size Pots are acceptable. The 24 volt supply specifically says up to 200mA of it can be used for external connections and it is probably what goes to the control switches for the digital control inputs DI1-4 as well.
 
mksj said:
Try the 9V battery.
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I am going to try 9v battery,but can I ask,if I want to purchase a 12v power supply for this application, what exactly should I ask for,that is if this is an option? . I am considering this only because I am not keen on disconnecting and connecting a battery every day.

Michael
 
Battery is only to rule out if there is an issue with the VFD power supply and for diagnosing why it isn't working. Just about any small 12VDC power supply will work, you would want one that can run off of your incoming AC power which I assume is 240VAC. The tach does not take much power (a few watts), so unless you want to add other LED 12VDC lighting then all you need is something small or a wall wart type if you want to plug it in (500-1000 mA or 10-25W). Something like the Meanwell HDR-15-12 or HDR-30-12 if you want to put it in your VFD cabinet.
 
Hi @Suzuki4evr
I too would recommend one of the smaller Meanwell supplies. The come in multiple voltages and multiple current outputs. One would run both your sensor and your display, if the display will work at 12V. It is the easiest way to go and they are cheap. However, if you do not have a place to put it you could use a small circuit board and with a three terminal voltage regulator, integrated circuit, like an LM7812. (there are other manufactures with different numbers for the same thing) You would want to add a capacitor to dampen any noise, but you might even get by without it. Also on Amazon or ebay, but you will probably have to buy more than one as they are so cheap. However, if you are not comfortable doing circuits then stay with the Meanwell or equivalent.

You can link to a data sheet at: http://www.datasheetcafe.com/lm7812-datasheet-voltage-regulator/

If you look at the schematic on Figure 3 of my post you will see I used one in my VFD conversion to drop the 24 volt supply voltage down to 12 volts. I labeled it P1 on the drawing. This thing will output up to an Amp, if it were available from your 24 volt supply, so you would not need a heat sink for it. It takes 24 volts in and outputs 12 V. Your Hall device probably needs about 50mA or so so 0.050 x (24-12)= 0.6 Watt the LM312 would have to dissipate. They make other versions of the device for other voltages. https://www.hobby-machinist.com/thr...tronic-components-pm1440gt-vfd-3-phase.95058/
 
So I tried the 9V battery today,but nothing happened, I don't know if the battery was deffective. All I know is that when connected to 24V the display comes on showing 4 zeros,the sensor lights up an flahes and a reading shows quickly when the spindle is turned by hand and when I run the motor 4 dashes apear. I will try a new battery.
 
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