DIY Stir Plate Problem.

[jay7792]

Hi Guys, I have collected all of the items needed to make my own Stir Plate but am having trouble understanding the wiring schematic

I have not got a clue when it comes to understanding these diagrams

I can see the +side of the fan but where does the - connect???
My pot has 3 pins on it, are they the 3 circles at bottom of diagram???

Does the 330 resistor connect between the out and adjust pins on the LM317???

Where does the capacitor connect to, is it between the in pin on LM317???

I am so sorry to ask so many questions but I really want a stir plate from a proven design, can somebody please try to explain the above diagram is complete dummies terms

Jay

 

[Monster Mash]

I've built 8 of them like this for me and other people and they work great.

EDIT: I just noticed I put AC instead of DC. It is all DC...

 

[WoodlandBrew]

On the first post I would switch two resistors.

On the second post, you might have a problem with the pot burning out if you leave it at a low resistant setting. If you add a series resistor so that as the resistance goes to zero the power dissipated on the rheostat will stay within the manufacturers limits. Also, most variable resistors I have seen the center tap is the wiper, so you would want one of the two on the end, and the center tap. If the knob works backward from what you would like then switch it to the other end.

I made a few stir plates a week ago and didn't bother with a speed knob. By selecting an appropriately sized stir bar it works just fine. (and used a 1A 9v wall wort instead of a 12v)

 

[LoloMT7]

The above post and diagram would work just fine (you could burn out the rheostat after time that is true)

Note: Do Not ground the Rheostat! Some people make that mistake and it will definitely burn it out. You want to go into and out of the switch and rheostat in a series configuration. I like to think of it as one big loop. Power out of wall adapter into switch then back out of switch into rheostat then out of rheostat into fan. Then power travels through the copper coil in the fan and comes back out the negative wire and needs to complete the circuit so it goes straight to the negative wire of the adapter. Loop complete... and really if you get technical i should have left from the other side as DC current actaully travels from Negative to positive


I did a very basic one and didn't use a rheostat or a power switch:

I just found an 8v dc wall adaptor cut the end off identified which lead was + and which one was - (if you get a positive reading with your voltage meter testing the wires then you have identified them right) and connected them directly to the fan leads.

8V DC seems to be the right speed for mine, and I figured I didn't need a switch if i could just unplug it

 

[day_trippr]

Referring to the diagram...

- Just above the word "speed" is a GROUND symbol. The negative pole of the power supply, one side of the .1uf capacitor, one leg of the potentiometer and the negative side of the fan all connect together on that wire, which will be the current return in the system.

- For the pot, the GROUND connection should be to one of the two outside pins. The middle pin connects to the ADJ pin on the LM317 (typically the center pin) and one leg of the 330 ohm resistor.

- The resistor connects between the LM317 OUT and ADJ pins as drawn.

- The capacitor connects across the power supply leads. It's there to reduce input noise before it hits the LM317

Really, don't over think this, just follow the "plumbing". The three things to take care about are the polarity of the power supply, the polarity of the fan, and the pin-out for the LM317. If you get these right you should be golden...

Cheers!

 

[Monster Mash]

On the first post I would switch two resistors.

On the second post, you might have a problem with the pot burning out if you leave it at a low resistant setting. If you add a series resistor so that as the resistance goes to zero the power dissipated on the rheostat will stay within the manufacturers limits. Also, most variable resistors I have seen the center tap is the wiper, so you would want one of the two on the end, and the center tap. If the knob works backward from what you would like then switch it to the other end.

I built these over 6 years ago and they still work perfectly. They need to be run at about half speed because full speed is too fast and sometimes throws the stir bar after the yeast builds up.