Electronics help????

[abunaitoo]

Any electronic hobbiest out there????
Have a problem I need help on.

I have an old Lyman Auto scale powder measure. Just can't get it to work.
Problem I'm having is the fast feed tubl is feeding to fast. So fast that it flies past the measured setting.
There is an adjustment to stop the fast tube sooner, but it's adjusted as far down as I can go, and it still feeds to fast.
What I want to do is slow down thw fast tube.
It's a 9 volt DC motor. Both motors are the same.
The slow motor get 5volts. The fast motor get 9 volts.
I switched the wires around and the motors are the same.

I had a potentiometer from Radio Shack that I tried. It's rated at 5k-Ohm, 500VDC-.05w.
It worked, but the range was to narrow. I'm sure it's the wrong one for this voltage.
Any idea what I should get?????

I was also thinking that just a resistor, in line, might work.
If it would work, what reisitance should I look for????.

[RobsTV]

Without more details of the motor, it will be just trial and error. We do this all the time with computer fans to reduce noise.

Potentiometer is in series with motor, correct? (not across the motor wires, but one wire is cut and the pot is connected to the two cut ends or wire.) You then need to measure the voltage drop across both the motor leads and the pot. Adjusting pot should increase voltage on the pot, while decreasing voltage of motor. Sometimes you need very little resistance to make major changes, and other times you need a lot of resistance. Max to min might be 100 ohms or 100,000 ohms (100k). I usually use a pot to find a close value, then change it out with a fixed resistor. Make sure the pot or resistor stay cool to the touch.

[jmorris]

If you want a fast and easy way to drop voltage put a diode in one of the wires. Each one you put in series drops about one volt. So if you want to go from 9-5 volts try putting 4 in there.

[rda72927]

+1 on RobsTV advice. Please let us know how it works...

[abunaitoo]

I wired the potentiometer(POT) in series.
Wired terminals #1 and #2 to the motor, #3 to the power.
I need to turn the dial almost to the end to get the motor to start. I'm thinking I need a POT with lower resistance.
The range is so narrow, I can't get it set to where it's consistant.

I tried a bunch of resisters that I took off of a board I had.
Most did nothing. Some wouldn't let the motor even start.
Have no idea how to read the color codes.

I'll try the diode thing. Board has a few of them on it.

As you can tell I have very little idea what I'm doing.
But I'm trying.

[1hole]

I 'spect you would do well with a series pot in the range of 25-100 ohms. As you now know, 5K is WAY to much resistance for that kind of job.

[Iron Mike Golf]

Can you make a reducing bushing to cut down the powder flow rate out the end of the tube? That how the 1200 DPS 3 deals with ball powders that overshoot like that.

[abunaitoo]

I'll look for a 25-100 POT at Radio Shack.
Thanks

Never thought of making the hole smaller. Might be something to try if the POT dosen't work.
Thanks

[hunter64]

Your on the right path, you just need to narrow things down a bit.

First off you will need a volt/ohm meter, pick up a cheap one for 10 bucks if you don't already have one.

You said you had to turn your pot almost all the way to the end to get the motor to start which means the pot has to much resistance.

When you have an ohm meter, turn it on again and adjust the pot till the motor just comes on and is about the correct speed that you want. (You have a 1 turn pot which means it goes from 0 to 5000 ohms in one turn of the knob. You really need a 10 turn pot which means it takes 10 turns of the knob to go to 5000 ohms.)

Once the pot is adjusted to about the correct speed as best you can, turn the power off and without touching the knob on the pot desolder all three wires to the pot.

Now with your ohm meter check between posts 1 and 2 and tell me the ohms reading and also tell me between 2 and 3. You must desolder the wires to take this measurement otherwise you will get a false reading.

Once this reading is established we basically substitute the correct value of resistor or if you want it adjustable we can make your pot work for you.

Take these measurements and post your results and I will let you know what the next step is.

[jmorris]

I was trying to keep it simple when I suggested the diodes to progressively reduce voltage. If you are wanting to be able to adjust it the best way is to build a voltage regulator. RS part # 276-1770 would be the main part then you can trim it with a small pot.

[hunter64]

You said you had a few resistors on the board. Look and see if one of them has any two colors and then a brown band as the third. So it could be red,red and then brown etc. If you find one then solder it in parallel between pins one and two of the pot and that will knock the resistance down to where it should be.

[abunaitoo]

I will try and take some readings.
I will look to se if I have the correct resistor.

How would I hook up the RS part # 276-1770 ????

[hunter64]

That part is a 7805 voltage regulator and is a great choice if you have a high current situation. I am not sure you need one but I have no idea how much current the motor draws. See if you can find a current rating on the motor and if not then desolder pin 3 of the pot and put your volt/ohm/amp meter in series with the pot and the wire and see how much current the motor draws.

To read the resistor color code go to http://www.ealnet.com/m-eal/resistor/resistor.htm and punch in the colors and it will tell you the value. Putting a low ohm resistor in parallel with pins one and two will cut the ohm reading down to slightly less than the lowest value of the added resistor.

So putting a 480 ohm resistor in parallel with you 5000 ohm pot with give you about 438 ohms http://www.sengpielaudio.com/calculator-paralresist.htm

If your motor doesn't draw that much current we can get away with the resistor, if it draws a lot of current then we will deal with the 7805.

[abunaitoo]

I went and got a 1k-Ohm-15 turn POT for Radio Shack. It was the only one they had in stock.
Hooked it up and it worked ok. It's very sensitive. 1/4 turn will keep the motor from staring from where I like the tube speed. Two turns from stop to full speed.
Anyway I took the readings and got:
Termanal #1 + #2 = .425
Termanal #2 + #3 = .612
Forgot to get the voltage reading.

I was looking closer and thought to myself:
"Self"... If I can make the fast tube stop sooner, it would keep it from over filling.
Looking closer I could see that if I made the slot the "eye" was riding in lower, it would stop the fast tube sooner.
Got the Dremal out and made the slot lower.
It worked. BUT!!!
Without slowing down the fast tube, it still would feed to fast, and jump past the full mark.
So. It seems to be working now. Haven't trued to load with it yet.
I would like to find a POT that would be less sensitive.



Your on the right path, you just need to narrow things down a bit.

First off you will need a volt/ohm meter, pick up a cheap one for 10 bucks if you don't already have one.

You said you had to turn your pot almost all the way to the end to get the motor to start which means the pot has to much resistance.

When you have an ohm meter, turn it on again and adjust the pot till the motor just comes on and is about the correct speed that you want. (You have a 1 turn pot which means it goes from 0 to 5000 ohms in one turn of the knob. You really need a 10 turn pot which means it takes 10 turns of the knob to go to 5000 ohms.)

Once the pot is adjusted to about the correct speed as best you can, turn the power off and without touching the knob on the pot desolder all three wires to the pot.

Now with your ohm meter check between posts 1 and 2 and tell me the ohms reading and also tell me between 2 and 3. You must desolder the wires to take this measurement otherwise you will get a false reading.

Once this reading is established we basically substitute the correct value of resistor or if you want it adjustable we can make your pot work for you.

Take these measurements and post your results and I will let you know what the next step is.

[popper]

Wait a minute. Motorized powder dispenser with fast and slow motors to drop & trickle into a pan or case for weight measurement? Real question should be WHY is it too fast. So you add a pot or tweak it now, what happens if it decides to change speed? An integrated unit with electronic grains measure - who know if that's correct? Motors don't just decide to run faster. Get it fixed right or get a new one.

[hunter64]

I would get a resistor around the 1000 mark and put it in parallel with pins 1 and 2 and that should give you a little better adjustment, not so sensitive.

[abunaitoo]

Thanks hunter64.
I've got a bunch of boards with resistors on them. I'll see what I can find.
If not, iy's back to Radio Shack.

[abunaitoo]

Installed the resistor.
It now works like it should.
Thanks hunter64 and the rest who had suggestions.
This place is great.

[hunter64]

Glad it works.

[abunaitoo]

Loaded up 80 rounds tonight.
I can't say it's any faster than dumping and weighing, but it does take out one step.
I'll try tweeking the speed a little, but so far it's working great.