Finley did it, home made speed control

well the noise comes from the motor, but a computer power suplay case is a good idea, but there might be a dust problem
 
Finley, Great post!!! My gosh..it is so simple! and inexpensive.

This should work great for 90V DC motors.

Have you tried 220VAC input...? The output would then become 180VDC...but I'm not sure if we would have to change some r values..?

What do you think?

-Rob
 
well, i think that 180 might be ok because when i was using the full bridge it was showing 150, so 180 is not that far off, but onley testing will tell. yes i gess there is alwase people to say its to simple and that it does not compare to a profesional speed control, well there probabely right but you cant build one of thoes speed controlers for 5-10 bucks. and for what i need its just fine, you would no beleve how long it took me to find something that worked. i will put togather a price and parts list, i did find that i do need a little biger pot for the control. i was using a small one that was made from plastic but to day i say some flashes of light coming from inside to pot, does not suprise me, it was a small pot.
 
A box to surround the circuit will only help to reduce the electrical noise that is radiated through the air. This circuit works at such a low frequency that virutally all the noise would be conducted out the power cable to the supply. TV's, radios and stereos in your house, and in your neighbor's house, may emit strange noises when you run your motor.

For safety's sake, at least connect a fuse (say 15A fast blow) in series with your power switch. Otherwise we may suddenly stop hearing from you.

Phil
 
JT

I just noticed that in your last post you said that there were flashes of light coming from your pot. You have probably exceeded the voltage rating of the pot and it was arcing inside.

Since the pot is connected to lethal voltages, make sure that you use one that has a plastic shaft to avoid electrocuting yourself.

Phil
 
Have you measured the output frequency through the full range yet? That will give you an idea of what fequency the noise will be. The noise problems can be fixed but you have to know the freqs. first.
 
pso said:
JT
Since the pot is connected to lethal voltages, make sure that you use one that has a plastic shaft to avoid electrocuting yourself.
Phil
Click to expand...
Phil
forgive me if I'm wrong and please correct me if so
but he does have a diode on the 120 line side between the pot and the line in
this should now be DC voltage which should be ok to handle being direct current now (on the pot side),
it's the alternating current ( AC) that is dangerous right??
taking into consideration nothing happens to cause it to short to AC again..
I should think it should have a diode in the neg 120 line also to make sure the line isn't reversed went pluging it in ...
clue me in if I'm wrong..:o

I did have some big questions on the first set up with the rectifier wired that way
because of the way the current is shown flowing..
 
NickWheeler said:
I know Finley, and I'm not a bit surprised to hear that that bastard did it again. :eek:
Click to expand...
Nickey........glad to see your full-time job hasn't spoiled your unique sense of humor. :D

Robert
 
B Finnigan said:
With enough amperage either AC or DC can ruin your day if it travels through any vital organ(s).
Click to expand...

OK if so
lets sort fact from fiction..
why can I or anyother welder weld with dc at 30amp + and only get a good buzz if grounded real good,,
as well as many welders well tell you,, if welding units were that dangerous you'd have a lot of dead welders around or not around which ever way you want to look at it.. :confused:
if it were AC 1 amp would/could dump you real fast grounded as well..

this is why cars and trucks are set up with DC and not AC, although the alternator is AC but it converts it to DC through the rectifiers
if DC was hamfull here too you'd have a lack of auto mechanics also..
a car battery can have well over 700 dc amps you can grab both posts and get nothing that will hurt you..not enen a tinggle and your heart is right dead center of the two contacts, a closed circuit,,
but these things are protected by manufactures that know the safety side of it by not letting the ac leak into the DC..
kids don't try this at home..
 
Without getting too technical a welder may be 30+ amps but the voltage or pressure is very low, same with a car battery. However if you had sweaty hands you would not get just a tingle, flesh would be missing and what remained would smell like burnt steak. Our vehicles electrical system is converted to DC to charge the battery, they cannot be charged with AC. It is not about saftey.

DC voltage is just as dangerous as AC given enough amperage and the right conductive potential. Have you seen what one quick arc can do to the battery terminals? That is only 13-14 volts but 400-700 amps. You can lick a nine volt battery and get nothing but a wierd taste since it is only 1/2 amp.

At low voltage our flesh is not the best conductor and the fact that more welders/mechanics have not been eletrocuted is more pure luck and circumstances. A lightning bolt is pure DC current and kills people all the time. It is very dependant on the path it takes, does it travel along the skin enrout to a ground or through the brain and heart.
 
I'd be inclined to listen to Phil (pso). Last I knew he'd been a working engineer specializing in power control and drive design for some time. His comments aren't based on speculation so much as years of experience doing this stuff professionally. Of course that's just my opinion which is worth every nickel you paid for it :)
 
Safety is related to the voltage found in the circuit, not whether it is AC or DC. UL, CSA and all the other international safety agencies consider anything over 50 Volts AC or DC to be a hazard. This means that the designer/manufacturer of the product must ensure that there is no reasonable way that the user can come into contact with the circuitry with the lethal voltages.

It only takes a few thousanths of an Amp of current flowing through certain parts of the human body to cause death. Normally, the human body is not a very good conductor so it takes a relatively high voltage to cause a lethal current to flow. The voltages present on your car battery, on the output of a welder and on the output of all those "wall wart" adapter transformers for your household electronics have been chosen to be low enough not to cause lethal currents to flow.

With the circuit posted (http://www.footbagsewing.com/uploads/newmotorcontrol.GIF), there will be voltage peaks that reach about 156 Volts, 60 times a second. The connection shown running along the bottom of the drawing should normally connect to the neutral line of the supply. The neutral is usually at or near ground potential but can never be considered safe to touch. It is possible for the branch circuit in the house to be wired incorrectly with the hot wire going to the neutral prong of the receptacle. Also, if there is a short circuit in some other piece of equipment connected to the same supply, the neutral can have significant voltage on it. I believe that the transformer in a welder provides electrical isolation between the supply and the output to get around this problem.

The latest circuit, with a single diode rectifier, will draw asymetrical currents from the supply at a frequency of 60 Hz. Since the current levels can be quite high, this alone may cause distortion of the voltage waveform and cause other equipment in the same house and neighboring houses to experience problems. Depending on how "clean" the physical/electrical layout is of the circuit is, there will likely be bursts of higher frequency noise in the range of 10kHz to 1MHz. These bursts would occur each time the SCR is turned on and off (120Hz). Getting rid of noise like this typically takes up 10% to 30% of the R&D effort for a product involving power electronics.

I don't want to be a wet blanket or sound like the "Safety Nazi's" here at work but safety is no joke. Some of the stuff being proposed here is simply dangerous. The "savings" is often just not worth dieing for, literally. A new maintenance guy, with sufficient experience (cheap labor), was electrocuted two years ago. Since then, OSHA have been over this place like flies on $h!t.

Phil
 
It only takes a few thousanths of an Amp of current flowing through certain parts of the human body to cause death.
Click to expand...

from alternating current not from low voltage DC amp's

I don't want to be a wet blanket or sound like the "Safety Nazi's" here at work but safety is no joke. Some of the stuff being proposed here is simply dangerous.
Click to expand...
I agree Phil and you are talking about in both cases AC

I mentioned if it's converted to DC..as a question..and then went to facts , what if.. hence let me have my say..on DC fact from fiction

The latest circuit, with a single diode rectifier, will draw asymetrical currents from the supply at a frequency of 60 Hz. Since the current levels can be quite high, this alone may cause distortion of the voltage waveform and cause other equipment in the same house and neighboring houses to experience problems.
Click to expand...
yes I understand this , this is why I asked and thought it better to have another diode in the neg line it was a question, I would rather see a full rectifier in there to be safer on the other side, what I don't understand is the other devices in there and what they will do to DC current and if they may cause the DC to convert back to AC with I agree could or can kill you.
cars I know electronics as this I'm iffy on..

I'm not looking to upset or badger anyone but just to inform, you are scaring the hell out of people and I'm saying it don't have to be that way with a little know..considering DC only...humor me a little in a not so humorous issue..

lightning,
household current ,,
and automotive electric ..

for the major three electricity's we are talking about

these are three totally different animals and should never be confused with each other..

lightning will kill you from the heat generated from the voltage most of the time more than anything else, it will/can dehydrate you stopping your blood in it's tracks, generated from the HIGH thousands of voltage itself, and certainly not from the little dc amp's it generates

you hear of the shoes melted to ones feet that's not from the little DC amp's
from lightning that is very high voltage doing that.

Phil I don't doubt in curtain rare circumstances that anything can kill you but I stand a better chance of hutting myself by dropping a car battery on my foot then it ever electrocuting me ..

but you know as well as I, it's alternating current that disrupts the heart electrical signals that people have to worry about

with the automotive biz .. they is no way on this green earth that OSHA
the insurance companies or lawyers to name just a few would ever let car batteries set on open selves at floor level (where BTW kids have access to them) of all the stores that sell them, let alone sell boaster cables to anyone that wants them and for one minute thinking it was dangerous to the public at large..

I have worked in the auto biz and as an auto diesel and truck mechanic for well over 30 years , still do to a point, where I am and still a licensed State inspection mechanic and an owner of a licensed state inspection station
I can prove that too..just so I can prove what I have done for the past many years if there is any doubt of what I know and do..

yes indeed
I have shorted out batteries with a big flash and in-turn messed with live wiring in those systems with sweaty hands an brow and never got a shock from me being the dead short..a screw driver is a very good conductor from this that is heat generation but from a dead short/ground with it not the hands..

in turn I have gotten lifted by the high tension side of the ignition system where you have 12 volts going into a primary side of the ign coil then with in it is converted it to well over 15000 votes, but it's not alternating current it will zap you but you stand more of a chance of banging you head on the hood and hurting yourself that way, then electrocution from even that type of shock,
even with wet skin, it is
such a poor conductor it's the reason you don't have sealed hoods on,,,,
how many cars and truck on the road today??

yes the battery is a storage unit for starting the car and short term accessory use only,
but why is it not, that the rest of the cars lights, radio, cigarette lighter and all the rest set up for 110 ac..
the alternators are capable of it, and they ( the manufacture) know the system would be more efficient if done that way,,
Why? because it's 12 volt DC and is in most part very very very safe,, also you'll find that the
fwiw charging systems in cars are set up to deliver 14.7 volts to the battery and up to as much as and more in some vehicles 100 amp's...I've attended a few electrical clinics myself on this stuff..

if you really feel I can get burnt, shocked real bad or even killed by wetting my fingers and touching the terminals of a car battery, I'll prove it to anyone
with a volt meter showing what I'm touching, I've done it many many times one way or the other and nothing..if one man nowadays got killed from a 12 volt battery or for that matter any part of the cars electrical wouldn't you think there would be a grand investigation by every agency concerned and the media to why and what to do so it would never happen again? that's why osha is on your companies case yes AC is a big problem that's why..you put locks on the boxes while the wiring is worked so on why not the hood of any car? anyone can get in there man woman and kids...WHY

I'm not saying anyone should just mess with anything they do not under stand because being safe then sorry always apply,, but I know the auto business inside and out and it's electrical systems..

you don't have to be scared to change your car battery or boost your own car
(positive to pos negative to negative people) or you will cause a dead short and screw up your charging system..

thank you for your time on this..it is interesting..
 
well i tuched the output to the motor while i was wireing it to the speed controler and i felt a tingle but nothing like when i was working for my dad and i was installing plugs in the wall and the power as not sapost to be on, well it was. now i have goten zaped by 110 quite a bunch and it does not bother me that much. from what i have read it is the amps that kill you but for it to do that you need to have somthing like 70-100 mila amps strait acros your heart to stop the muccles which are run by electrial pulles from your head. but for the most part electricty travils across the skin and not through the body. i have by axcadent shorted an ac welder through my body, ground in one hand and the welding clamp in the other. i hit the floor but was not hert.
 
JTknives said:
well i tuched the output to the motor while i was wireing it to the speed controler and i felt a tingle but nothing like when i was working for my dad and i was installing plugs in the wall and the power as not sapost to be on, well it was. now i have goten zaped by 110 quite a bunch and it does not bother me that much. from what i have read it is the amps that kill you but for it to do that you need to have somthing like 70-100 mila amps strait acros your heart to stop the muccles which are run by electrial pulles from your head. but for the most part electricty travils across the skin and not through the body. i have by axcadent shorted an ac welder through my body, ground in one hand and the welding clamp in the other. i hit the floor but was not hert.
Click to expand...
well i tuched the output to the motor while i was wireing it to the speed controler and i felt a tingle
Click to expand...
:rolleyes:
well you don't have pure DC then,it could be a back feed from the neg side it's my point in all this..it's not a safe set up..it's telling me.

I'll guaranty you if you are grounded properly 110 will kill you
as a kid and a fool I too messed with 110 AC just for the fun of it grabbing 110 wires it can take the bend out of your elbow real fast for sure..it's not recommended for anyone to do
as I said as a fool kid, if I was grounded by bear feet to a wet ground I wouldn't be telling you this right now,and I truly believe that,,, the lord is watching over the both of us and we should thank him for still being here don't push your luck John. luck runs out randomly . I'm talking DC where almost nothing will go wrong..key words to watch out for is almost never
john can I ask you your age?? like Phil said manufactures put out as safe a product is possible and what you are doing should be do with much caution

the concern here was and is you came in here with out any of the cautions
advised and you need to remember 100's are looking and could be trying this out, caution to all...
 
Doesnt matter whether it is AC or DC,with enough voltage to pass thru the body,and enough amps behind it,you will die from either.
That is fact not fiction.
Car batteries do not have enough voltage to pass thru the body,a welder is getting close but not quite enough.
You can let your guard down with DC if you want,its your life you are gambling with.
 
You may have felt the DC pulses which would give you the tingle. You can feel pulsed current at low voltages just because it has more contrast on your nerves.

I have learned enough about AC and DC to respect both and not take chances. After being a firefighter/EMT for thirteen years I have had the oppurtunity to see what electricity can do, both AC and DC to the human body.

If anyone wants to think that DC is harmless then do so at your own peril. I have built enough electronic circuits that the one posted here is safe if built correctly (eclosed, grounded and fused).
 
Toxey said:
Doesnt matter whether it is AC or DC,with enough voltage to pass thru the body,and enough amps behind it,you will die from either.
That is fact not fiction.
Car batteries do not have enough voltage to pass thru the body,a welder is getting close but not quite enough.
You can let your guard down with DC if you want,its your life you are gambling with.
Click to expand...
I think if Finnigan mentioned in the first place
AC or DC,with enough voltage
Click to expand...
this would not have been such a thread :(
yes if enough of both agreed at the same time and your not getting enough of both the in automotive..in the DC end of it..thank you

Phil mentioned the safety guide line at anything over 50 amp and I mentioned up to 30amp with the welder .. agreed yes. but you have welders everyday using
large drag rods that exceed 50 amp, but as the government goes they set the guide lines to a real safe limit..

the reason I mentioned the three types of electricity was if we look
at them they are different, in this combination..

lightening is high voltage with low amp's you don't have both, you burn or cook because of it heat if hit, it's not electrocution.

with a car on the primary side ( the Battery side) of the ignition you have low volts and high amps (DC)
not both,, safe
on the secondary side of the coil's ( to the plugs ) you have high volts and low amps
still not both, a big jolt but not harmful unless you hit you head or something else from the shear getting caught off guard from it by jumping you..

I will mention, if you have a distributor-less system the shock will hurt the hell out of you, the spark can jump over 3" again banging your head on the underside of the hood will do more damage to you .this is at a higher voltage than the HEI (high energy Ignition) system I mentioned before and we've known from the 80's into the 90's

house hold current, again is the most dangerous we worry anout with the both, higher voltage, higher amp's and being AC..

summed up again if you do not know what you are doing and fully understand
electricity, don't,, touch..
 
Dan Gray said:
lightening is high voltage with low amp's you don't have both, you burn or cook because of it heat if hit, it's not electrocution.
Click to expand...

I was curious just how much amperage a lightning strike can have and I was surprised that is can be 200,000 amps. The voltage is more then enough to interupt and de-syncronize the cardiac muscles (V Fib) which is electrocution. With 200,000 amps of muscle behind it you get some good cooking heat too.
 
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