diy seio controller*speed controller

[A.T.T.R]

anyways need help finding a double pole double throw ( or double pole single throw ( ill use two of them but prefer dpdt) solid state relays capable of being triggered at 5.5 volts with a load of 120 volts. and able to run at 60 or more hz
anyways thanks for any help.. i suck at finding info on specific parts!

[Donw]

Originally posted by stugray
As a matter of fact it would work.

If you pulse an AC motor on for 1/2 second ( 30 AC cycles ), then off for 1/2 second ( 30 more AC cycles ), then you are effectively driving the pump in a pulse width type of fashion.


Stu

I do this with my aqualifter ato and it works well. Never thought about doing it with a pump. Have you actually tried it with a powerhead?

Don

[ShawnJones]

Just use Digikey, I found a few on there, you can narrow down the search to find exactly what you need.

Digikey Link

Shawn

[fatrip]

are these the types of relays you are refering to... http://www.mouser.com/search/refine....nal&Mpcn=65308
....low signal SSR's??

[ShawnJones]

Those looked like mechanical relays to me. These are solid state.

http://www.mouser.com/search/Refine....RefType=Header

Shawn

[fatrip]

some are SS some are Mech but they are serface mount...and he probibly doesnt want that...srry...

[stugray]

A.T.T.R.

"your talking about cutting off ac power partway into a wave.. that is what dimmers do. they only alow parts of the sine wave out."

No I am NOT talking about cutting off the ac power partway into a wave, that is what a SCR does, and it is not good for pumps while it works great for incandescent lighting.

By toggling the AC power on and off ( but allowing MANY full AC cycles through ), you would control the motor speed using Pulse Width Modulation of the AC signal. Since motors take time to speed up when power is applied, and time to slow down when power is removed, you just need to find the "sweet spot" for your particular motor. And by experimentation you could find the proper PWM rates that could control the speed. An example - My bathroom fan takes many seconds to spin up to full speed. I can control it's "average speed" just by standing there and turning the wall switch on and off.

You have said yourself that you know nothing about PWM, but you do nothing to go learn.

Many of us on this thread have tried to "assist" you in a nice manner, but you apparently are reluctant to listen.

An example of that is I mentioned that you can get SSRs from www.mpja.com ( for as low as $3 a piece), but you dont see what I am trying to say.

All I can say at this point is "Good luck with your approach".

It's a lot like my favorite saying at work .... "Full Speed ahead, direction to be determined".

It seems that you are so set in how think it "should work" that you are deaf to all the ones who say "it doesent work that way".

Carry on then.

Stu

[A.T.T.R]

stug ray. i looked on that site and found a bunch of things that ment nothing to me ( no specs. atleast that i could find)

as for why im going this way i have the probram done already. and no one said it WONT work they said it may not work

and guess what. i want to TRY my idea. if it DOSNT work i already have the relays and can CHANGE it to a way that does work. whether that be your on off of a normal 60 hz. or PWM of each sine wave. ( which looks hard) and yes every time that you mention somthing i do read up on it . i look at it and think about it. but in the end. i would really like to try my way since i wasted so muc time coding it!!! ( if i did what you were just talking about i could of cut my code in atleast half)

[A.T.T.R]

oh also re read my post... half way in i relized what you were saying

[stugray]

Sorry, the mpja webstie is a bit hard to navigate:

http://www.mpja.com/prodinfo.asp?number=16824+RL

This SSR will do 1 A at 240V with a 5VDC control signal NO "contacts".

Stu

[A.T.T.R]

ahh very cool


i came to a sad relization. DPDT ssr;s dont exist as far as i can tell lol
but i can use 2 spst NO and 2 spst NC's to get the same effect.

stug any idea on switching time on those relays? can it handle being turned on and off 60 times a second?

[A.T.T.R]

oh also i fotgot to say this they need to be DC outputs that one says AC only.

i guess ill look around when im awake tommorrow

[Donw]

Crydom makes dpdt but ac switching surface mount only. I did try the pulsing thing 60 cycles per second and it works very well other than the noise. I think if the impellor were stationary it would be quiet.
When they say pulsing is rough on a pump. What part of the pump is it rough on?

Don

[stugray]

Use the Digikey link above & search for:

Z2032-ND

It is a 1 A, 200V DC SSR, but it'll run ya ~$17 each


As for the pulsing the motor being bad for it: It is rough on a pump pulsing it constantly because 1 - it is mechanically stressed by the constant start/stop torques and 2 - Every time you apply or remove voltage from an inductive load ( relay, motor, solenoid ), apruptly, it causes a "reverse Electromotive Force" or EMF. The EMF must be handled with a reverse EMF bleed diode of transorb type of device. The Constant EMF spikes can cause heating in the motor &/or damage to the driving device ( FET or SSR ).

Stu

[A.T.T.R]

yeah the pulsing thing should work grat with the aqualifter tho since all it is is a magnet that pulls on sping to move a diaphram

[A.T.T.R]

now for a dumb question

why wont the AC models work with DC current? is it the same reason as capacitors where it just degrades them really fast

[Donw]

Originally posted by A.T.T.R
now for a dumb question

why wont the AC models work with DC current? is it the same reason as capacitors where it just degrades them really fast

They will turn on but will not turn back off.

Don

[ReefWreak]

Wow this thread is really interesting. I'm interested and definitely going to follow. A.T.T.R. arn't you a local down in SoFL too?

BTW It may not be good policy to argue/disagree with a rocket scientist (Stugray). Lol.

Sorry for the OT, please continue. I'll be following the discussion.

[hyperfocal]

Originally posted by A.T.T.R
now for a dumb question

why wont the AC models work with DC current? is it the same reason as capacitors where it just degrades them really fast

The type of AC motor used in powerheads like the Koralia requires the voltage rise and fall of AC to create the expanding and collapsing magnetic fields that actually spin the prop/impeller.

No AC, no changing magnetic fields, no spin.

[A.T.T.R]

oh i ment why wont AC RELAYS work on dc current ... guess i should of said that lol

[A.T.T.R]

now back to the drawing board unless i find a DPDT SSR im screwed unless i want to spend a bunch more for 2 SPST NO and 2 SPST NC dc relays

hmm.. ill figure something out to make it more cost effective

in the mean time if any one comes across a DC relay that will operate at 60 on offs a second and operate on 3-5.5 volts with a dpdt DC 120 volt load. let me know you will have saved the day!!!


stug i may buy two of those relays you posted along with the same one but NC ( if i can find them) just to test this thing out.. ill worry about cost later

[hyperfocal]

Originally posted by A.T.T.R
oh i ment why wont AC RELAYS work on dc current ... guess i should of said that lol

Ooops, my bad -- I should've looked back through the thread before posting. Missed the context of your posting entirely, sorry.

[A.T.T.R]

also they dont need to be a high amp relay. the pumps im using are koralias and they dont pull more then what 12 watts at 120 volt

[A.T.T.R]

yea im local parkland not too far from boca.

im hoping to have a working one of these before the next fmass frag swap so everyone who knows about this will be able to see it.


if not illthrow it on a tank at work

[stugray]

A.T.T.R

If you want to do Just DC and cant find a cheap SSR or "Output Module", you can just use a standard Power Mosfet like the IRF510/511 or something like it for a few bucks.

If you do a low side FET driver ( A mosfet on the return side of your load ), then it can be driven with TTL ( 5V ) signals. If you want a high side driver ( on the +DC side of the load ), then you need some extra circuitry to make it work.

You "used to" be able to get IRF510/511s at radio shack, but now it depends on your location.

Stu