Need help with Volts AC

[yathis]

I got me a 2 prong drill, I get 120Vac at the outlet, but 30Vac with the wires going into the switch. They are disconnected of course. I find that very odd.

Guage of wire seems to be 12 or 14.

I connect the wires up and I get 9V.

 

Its a 7A drill plug in style.

[W-L]

6 minutes ago, yathis said:

I got me a 2 prong drill, I get 120Vac at the outlet, but 30Vac with the wires going into the switch. They are disconnected of course. I find that very odd.

Guage of wire seems to be 12 or 14.

I connect the wires up and I get 9V.

 

Its a 7A drill plug in style.

What are you trying to do exactly, and the brand/model of the drill may help.

[yathis]

http://www.canadiantire.ca/en/pdp/mastercraft-5-8-in-7a-low-gear-mud-mixer-0541343p.html

 

It is a Mastercraft, 7A brushed drill, big and heavy, I used it for the deck. It has gears in the head by the chuck, and its heavy. Motor looks to be an innrunner style.

 

It just did not work and has been laying around for a few years, I opened it up and the one of the brushes has broken off. So I need to find a store to replace the brushes.

 

I was basically troubleshooting the drill, trying to figure out the switch.

 

The motor has two brushes with wires (red), the motor has 4 connections on the shell, 2 red, 2 black.

All the wires go back to the switch. The switch has what looks like a potentiometer but I think its to do with 3 settings as there is a diagram underneeth it. Its an E with the left part up, 6 5 4. The other half of the diagram, I believe is some sort of circuit, perhaps a diode. The whole switch mechanism is 2" x 1".

 

For the one brush, its more of a magnet, it broke in half, I am glueing it back together with instant glue, but the magnet needs to conduct electricity, so I am unsure as to a quick fix on that end. If I can find some metal flaked epoxy used for elec. connections at a decent price. Otherwise I am probably going to head to an electronics repair store and show them my brushes.

 

I find the switch intreging. Why would I get 120Vac at the plug end, then the cable disconnected, measuring Vac and get 30Vac, the wire itself wouldnt have that much resistance. I find that perplexing. Its a regular 2 prong plug in.

 

 

 

I am thinking about using it for a crude motor for my bicycle, until my ebike kit comes in the mail from China.

 

So I basically wondered at first if I hook up 120Vdc to the prongs if the motor would run. I have not done that yet, hence my opening it up and checking it out with my DMM. 30Vdc may work, may not. If anything the switch with its internal circuit would fry, then I am left with the motor itself. Which I again find intreging, 2 ground wires, 2 red wires on the shell, then the brushes.  I am used to brushless motors myself.

[W-L]

3 minutes ago, yathis said:

-SNIP-

Replace the brush if it's cracked or broken gluing it will add resistance and most likely heat it up excessively. They aren't very expensive usually < $10 for a set. As for the voltage the cord would be negligible in resistance really, the drop in voltage would be due to the speed control within the switch as most trigger controls still use a large mosfet I believe it was 

 

Ave does really good tool tear downs if your interested, and old unit but basically still the same concepts:

 

[yathis]

Ah great thanks for the YT link, I will start watching.

 

Basically I got the cord, regular  2 prong plugged in, black sheething like any other cable, covering 2 wires (B+W) goes to the switch. I disconnect them 2 wires, it now looks like any ole plug in cable that you would cut, strip back the wires, and measure. I would be expecting 120Vac, but no its 30Vac.

 

Video watching time.

[yathis]

OK I bought some new brushes from a Tool Repair place, installed them and the drill works great.

 

I thought I broke the brushes when I took out the stator/commutator, so I thought it was a switch. I remember a long time ago that the drill would work randomly for a split second and the broken brush explains that, so its not the switch.

 

That video channel you linked to, the guy is funny as fuck. He actually used 120Vdc battery to power a 2 prong tool, so they are universal motors. On my drill the further you depress the switch the faster the drill goes. This is a bonus for me, good for a throttle, I just got to extend the wires to the handle bar.

 

Next problem I have is should I hook up batteries to correspond to the RMS of 120Vac so 0.707 is 82Vdc or something?

[W-L]

6 minutes ago, yathis said:

OK I bought some new brushes from a Tool Repair place, installed them and the drill works great.

 

I thought I broke the brushes when I took out the stator/commutator, so I thought it was a switch. I remember a long time ago that the drill would work randomly for a split second and the broken brush explains that, so its not the switch.

 

That video channel you linked to, the guy is funny as fuck. He actually used 120Vdc battery to power a 2 prong tool, so they are universal motors. On my drill the further you depress the switch the faster the drill goes. This is a bonus for me, good for a throttle, I just got to extend the wires to the handle bar.

 

Next problem I have is should I hook up batteries to correspond to the RMS of 120Vac so 0.707 is 82Vdc or something?

Yes he's a pretty cool fellow, if you want to try the DC power it will work with a universal motor but get it close to 120V DC as peak 120V AC (RMS) will be around 170V. Just take the proper precautions if you want to experiment around, wouldn't want to accidentally short the batteries or to short it to yourself. 

[yathis]

170Vdc RMS would be 120V, you did it reverse

 

2 minutes ago, W-L said:

peak 120V AC (RMS) will be around 170V

 

Its not much of a jump to go from 82Vdc to 120Vdc, what an extra 4S. And yes my rule of thumb is I try to stay at or below 72Vdc, anything over 100Vdc and you gotta be very Very VEry VERy VERY careful.

[W-L]

11 minutes ago, yathis said:

170Vdc RMS would be 120V, you did it reverse

 

 

Its not much of a jump to go from 82Vdc to 120Vdc, what an extra 4S. And yes my rule of thumb is I try to stay at or below 72Vdc, anything over 100Vdc and you gotta be very Very VEry VERy VERY careful.

Yes it wouldn't hurt to go less can always add more later right.  Yes wrong way around