Calling All Sparky's (electrics) Need Help With Simple Schematics

[kelbygreen]

ok funky read your last post there is a hot side and a cold side if you want to cool something you put it on the cool side it draws the heat threw to to hot side where the heat sink is (hence the name) the fan will go on the hot side as well to cool the heat sink and cool it down a bit as for the direction of flow on it I am not sure if its best to push air threw the heat sink which may push hot air onto where you are cooling or draw the hot air away from the heat sink and push it out. blowing cold air onto hot parts works better but it its going to blow hot air onto the part you are cooling it may be less efficient so drawing the hot air away may be the go as it will suck cool air in from the sides rather then blow cool air directly on it

 

[mgill]

Great idea mate, I'll go pick one up tomorrow. I'm a really big noob with peltiers, basically I ordered two (specs listed above). I am going to mount an AMD heatsink/fan with some arctic silver 5 (thermal compound) inbetween the hot side and the heat sink. To move the cold air coming from the other side, I thought of getting some sort of tubing lined with aluminum foil or something, with a fan at the end sucking the cold air out into the cabinet. I noticed you were mentioning "cold" side heatsink, am I supposed to mount a heatsink on both sides of the peltier?

Thanks

No you don't have to mount a heatsink on the cold side, however you will increase the efficiency of the peltier slightly if you draw the temperature away from the plates quicker. I have used a fan based heat sink before for my applications but that has only been on the "heating" side of the peltier as I have wanted to cool to lower temperatures and the peltiers will only cool to about 25 degrees below ambient temperature (you can stack them on top of each other to increase the temperature they will cool down to but it dramatically reduces there efficiency.You can buy heat sinks which join together to form a square section which an 80mm fan can mount to (similar to what you are thinking of doing with tubing) I would definately try and draw the cool air off the peltier with some form of heat sink though. I used 2 of these for my current project (but that is major overkill) http://www.jaycar.com.au/productView.asp?I...mp;form=KEYWORD. I would just stick with a small fan/heatsink combo for the cooling side like you find for CPU's in computers. Is it a tightly seald enclosure you are making? Cause you will definately need to be careful of condensation and moisture if it isn't


Keep up the good work mate, your control unit looks really good, a very professional finish.

 

[funkyyyy]

ok funky read your last post there is a hot side and a cold side if you want to cool something you put it on the cool side it draws the heat threw to to hot side where the heat sink is (hence the name) the fan will go on the hot side as well to cool the heat sink and cool it down a bit as for the direction of flow on it I am not sure if its best to push air threw the heat sink which may push hot air onto where you are cooling or draw the hot air away from the heat sink and push it out. blowing cold air onto hot parts works better but it its going to blow hot air onto the part you are cooling it may be less efficient so drawing the hot air away may be the go as it will suck cool air in from the sides rather then blow cool air directly on it

Ah yes I get you. The compartment in which the peltier will be housed is completely isolated from the rest of the cabinet (hence the tubing to transport the cold air into the space I wish to heat / cool) So I don't need to worry about blowing the warm air back into the cabinet.

 

[funkyyyy]

No you don't have to mount a heatsink on the cold side, however you will increase the efficiency of the peltier slightly if you draw the temperature away from the plates quicker. I have used a fan based heat sink before for my applications but that has only been on the "heating" side of the peltier as I have wanted to cool to lower temperatures and the peltiers will only cool to about 25 degrees below ambient temperature (you can stack them on top of each other to increase the temperature they will cool down to but it dramatically reduces there efficiency.You can buy heat sinks which join together to form a square section which an 80mm fan can mount to (similar to what you are thinking of doing with tubing) I would definately try and draw the cool air off the peltier with some form of heat sink though. I used 2 of these for my current project (but that is major overkill) http://www.jaycar.com.au/productView.asp?I...mp;form=KEYWORD. I would just stick with a small fan/heatsink combo for the cooling side like you find for CPU's in computers. Is it a tightly seald enclosure you are making? Cause you will definately need to be careful of condensation and moisture if it isn't


Keep up the good work mate, your control unit looks really good, a very professional finish.

So you think I should mount a heatsink on the cool side with a fan drawing the cool air away from the peltier into the cabinet? As for dimensions, it is 1365x550x150mm. A decent sized space, I wouldn't say tightly enclosed at all. Thanks mate, I'm real proud of it to be honest. I've been putting it through it's paces and so far its working like a charm.

 

[mgill]

So you think I should mount a heatsink on the cool side with a fan drawing the cool air away from the peltier into the cabinet? As for dimensions, it is 1365x550x150mm. A decent sized space, I wouldn't say tightly enclosed at all. Thanks mate, I'm real proud of it to be honest. I've been putting it through it's paces and so far its working like a charm.

yeah, you definately want to try and keep those two sides of the peltier segregated and move the temperature away from it as quick as possible. I only wish i had seen your original post earlier. I have a USB interface board which I am using with some common electronic components to do a similar thing... read in temperature, turn on and off a peltier (and reverse polarity to it to make it either heat or cool a fermenter). I have also purchased an alcohol sensor which I have mounted into a modified airlock to constantly read in the alcohol concentration of the fermenter. The idea is I will take the data collected over a few brews, and see if I can correlate it to % alcohol in the fermenter. At minimum, I will be able to graph the fermentation process (temperature and alcohol reading for the whole brew and see the point where alcohol concentration no longer changes to determine that fermentation is complete) and control the temperature. I could have provided you with a parts list, schematic and some basic source code for software which you could have modified to suit your purposes, only trouble is you have already spent so much time effort and money on your current project.

I am currently rewiring the hardware at the moment off a protoyping board and into an enclosure and plan to have the first test done in a couple of weeks, at which stage I will write the graphing component of the software and see how well the peltiers perform!

 

[NickB]

As for your bayonet fitting, there should be four screw terminals, one labeled E (Your Earth goes here), One labeled L (Loop - don't put anything here) and two unlabelled opposite each other. One of these is for your active, one for your neutral.

YMMV, as I'm not a qualified Electrician (yet), just a lowly apprentice.

Cheers

 

[funkyyyy]

As for your bayonet fitting, there should be four screw terminals, one labeled E (Your Earth goes here), One labeled L (Loop - don't put anything here) and two unlabelled opposite each other. One of these is for your active, one for your neutral.

YMMV, as I'm not a qualified Electrician (yet), just a lowly apprentice.

Cheers

My socket only has two screw terminals |:

perhaps I picked up the wrong type?

 

[mgill]

My socket only has two screw terminals |:

perhaps I picked up the wrong type?

All plastic? Are they labelled A and N?

 

[funkyyyy]

All plastic? Are they labelled A and N?

Yeah thats the one. Will it not work?

One of my peltiers arrived today, rigged it up to a heatsink + fan on the hot side, did some testing.

The cold side after 5 minutes reached -9.6C..

This is AMAZING results however there is one slight problem that was mentioned earlier in the thread.

I had frost on it.. condensation ey. How do I combat this? Without compromising too much temperature gain.

 

[dmerrick]

The only sure fire way to prevent condesation is to maintain a temperature above the current dew point. To determine the dew point takes a fair few variables, but in a nutshell, high humidity = high dew point, low humidity = low dew point.

 

[funkyyyy]

The only sure fire way to prevent condesation is to maintain a temperature above the current dew point. To determine the dew point takes a fair few variables, but in a nutshell, high humidity = high dew point, low humidity = low dew point.

So you think putting a heatsink on the cold side with a fan ontop of it sucking the air from the cold side out into the cabinet would reduce this? Condensation inside of the cabinet isn't going to be an issue as the minimum temperature at which it will ever be set is way above any normal dew point (probably the lowest it will get is 10-15C.

 

[funkyyyy]

Okay in the mean time I have drawn up a diagram of the final solution. I found a large heatsink from jaycar with no fan mounts, how do I go about attaching two fans to it? (to blow the cold air off of the heatsink into the case)

Thanks

 

[NickB]

Yeah thats the one. Will it not work?

Your light fitting will work, it just won't be earthed, so make sure the rest of your system is earthed well - Because if a fault occurs in your fitting, there's no path for any fault current to run to earth. Take for example that your active wire becomes loose, or broken, and touches a metal part of the chassis of your enclosure. You'd want to make doubly sure you're correctly earthed, and running through the appropriate RCD.

Mind you, after flicking through the AS3000:2007 (Wiring Rules), I can't see exemptions anywhere for light fittings, meaning you would need a fitting with an earth point for your install to be to Australian Standard... I know that all new houses must have am earth run to every fitting.

Personally, I'd be getting a better fitting (what brand is the one you have??) form an electrical wholesaler or similar.


Cheers

 

[funkyyyy]

Your light fitting will work, it just won't be earthed, so make sure the rest of your system is earthed well - Because if a fault occurs in your fitting, there's no path for any fault current to run to earth. Take for example that your active wire becomes loose, or broken, and touches a metal part of the chassis of your enclosure. You'd want to make doubly sure you're correctly earthed, and running through the appropriate RCD.

Mind you, after flicking through the AS3000:2007 (Wiring Rules), I can't see exemptions anywhere for light fittings, meaning you would need a fitting with an earth point for your install to be to Australian Standard... I know that all new houses must have am earth run to every fitting.

Personally, I'd be getting a better fitting (what brand is the one you have??) form an electrical wholesaler or similar.


Cheers

There is no chance of it touching any metal as the entire encloser is made of tasmanian oak.

As for what brand, its a cheapie from Hong Kong. I will go and purchase one with a ground =)

 

[crozdog]

how do I go about attaching two fans to it? (to blow the cold air off of the heatsink into the case)

long screws or bolts? cable ties have been used for all sorts of things ;-)

 

[funkyyyy]

long screws or bolts? cable ties have been used for all sorts of things ;-)

Ah yes I'm going to have to find some screws thin enough to fit through the fins, or drill through the fins. Ha. Zip ties could work too, I used a few of them in the wiring of my thermostat =D

 

[NickB]

There is no chance of it touching any metal as the entire encloser is made of tasmanian oak.

As for what brand, its a cheapie from Hong Kong. I will go and purchase one with a ground =)

That explains it then. Those HK cheapies are likely not even to Aus Standard. Not sure how they can import them! Good idea getting a better quality unit. Even an HPM or similar from the Green Shed will suffice. As they say, you only get once chance with 240v....

Cheers

 

[funkyyyy]

That explains it then. Those HK cheapies are likely not even to Aus Standard. Not sure how they can import them! Good idea getting a better quality unit. Even an HPM or similar from the Green Shed will suffice. As they say, you only get once chance with 240v....

Cheers

Yeah there is such a mass of them on ebay. Although some of the cheap stuff coming out of there is great, my temperature controller came from HK. It was only $27AU and it works like a dream. Agreed, This is my first time messing with 240, and so far so good it's been great and worked well. I'd rather not blow it all from a crappy import bayonet socket, lol.

 

[mgill]

So you think putting a heatsink on the cold side with a fan ontop of it sucking the air from the cold side out into the cabinet would reduce this? Condensation inside of the cabinet isn't going to be an issue as the minimum temperature at which it will ever be set is way above any normal dew point (probably the lowest it will get is 10-15C.

if average temperature is 25 celcuis and humidity is 75% (not uncommon in summer) then you will see a dew point around 20 degrees celcius. You may want to look at some weather observations for your region and compare average humidity and temperature. If however you have an airtight case for the housing, you will be introducing no extra water vapour into the air under which you sealed the case. To further reduce the amount of water vapour, you could add a bag of silica gel.

 

[mgill]

Okay in the mean time I have drawn up a diagram of the final solution. I found a large heatsink from jaycar with no fan mounts, how do I go about attaching two fans to it? (to blow the cold air off of the heatsink into the case)

Thanks

If your controller has a timeout delay or two set points you can use the Peltier to do both the heating and cooling thereby eliminating the need for the ceramic heater (All you need is 2 x 240V relays, which you use to switch the polarity of the voltage to the peltier). Do you have a specification sheet for your controller?

If it doesn't you are going to be rapidly switching between heating and cooling constantly, and you will more than likely sit on the higher side of you temperature set point given that it is far more efficient to heat than cool and your cooling capacity is quite limited.