DIY Cool Bot Builders

[zazbnf]

Just saw this thread for the first time. I have been running a controller using 2 stc-1000's, a 12v wall wort, using a 1W 100 Ohm resister and a pulse width modulator for the heat source. It has maintained 55 degrees in a small walk in cooler for the past couple years. About $30 for everything. You don't need to do any modification to the A/C, just wire the 2 stc-1000 so that if either hits the set temp it cuts power to the heater(resistor). 1st stc-1000 probe hangs into the cooler and has a set temp of 55 degrees, when temp is hit contact opens and kills power to resistor. Second stc-1000 probe is placed into the cooling fins where the air conditioners temp probe was(you simply unsnap the air conditioner temp probe and let it hang down)I currently have it set to 40 degrees on the before it cuts out. Trial and error showed that it takes a a minute or so for the air conditioner to respond after power is cut off to the heat source and the fin temp can drop very fast during this time. The 1 W 100 Ohm resistor is heat shrinked to the air conditioner probe that was left hanging down earlier and connected to the 12v Power supply with the pulse width modulator set to a level to warm it up but not get so hot it might burn itself out or cook the air conditioner temp probe. The air conditioner runs when the "heater" is on and turns off when either stc has an open relay.

 

[4Doose]

I went to your site for the great info and it cant be found. Did you take it down?

I would love to view it if its still available.

Thank you.

 

[Case]

Hi Terry, I am converting part of the back of my van into a refrigerated unit as I deliver meats and produce to some of the local restaurants in my area. I need to keep the temp below 40* for food safety reasons. I plan on using either a window unit or an RV roof top unit to cool the compartment. Can I use the 2 stc 1000's for this purpose and if so how hard will it be to hook them up to the air conditioner? I am somewhat mechanically inclined but have never tried anything with electronics like this. Any info you could give me would be greatly appreciated.

Thanks,

Casey

 

[zazbnf]

Hi Terry, I am converting part of the back of my van into a refrigerated unit as I deliver meats and produce to some of the local restaurants in my area. I need to keep the temp below 40* for food safety reasons. I plan on using either a window unit or an RV roof top unit to cool the compartment. Can I use the 2 stc 1000's for this purpose and if so how hard will it be to hook them up to the air conditioner? I am somewhat mechanically inclined but have never tried anything with electronics like this. Any info you could give me would be greatly appreciated.

Thanks,

Casey

Might not be the best use for an air conditioner. While they work well for a cooler that is opened infrequently, I would assume delivering produce would mean the area was opened frequently over a short time period as deliveries are made to different restaurants.

A controller and an air conditioner have a hard time maintaining temp in this situation. It takes a while for the air conditioner to bring the box back into temp if the door is open very long or frequently. This is because it works by lowering the temp a few degrees then the compressor shuts off for a while to prevent the coils from icing over, then it will start up again and lower the temp a few more degrees before the compressor stops again repeating until the desired temp is reached.

 

[Tegra]

Guess it all depends on the size of the AC.

T

 

[bembel]

I'm currently testing a makeshift coolbot I put together. It involves two STC-1000 units in series, as stated in a previous post, but instead of connecting the a/c unit, the STCs trigger a small 5v light bulb.
I used two STC-1000 units, a 5v light bulb and a 5v power supply (old cell phone charger).
First, I connected the +wire from the power supply to the light bulb. Then ran the -wire to the first STC COOL relay; from there it goes to the second STC's COOL relay in series, and finally to the other pole in the light bulb. Cover the light bulb with foil, attach the A/C unit's temp probe to this fixture and cover with foil again.
Place the temp probe of either STC inside the A/C's evaporator fins, set the STC to 32. This will prevent the evap from freezing out. Use the other unit's probe as your room temp sensor, set it to whatever your target temp is.
Set your A/C to the coldest setting.
The idea is, just like with the coolbot, to trick the A/C into thinking the room is warmer than it really is, by heating the A/C's probe with the light bulb or whatever heater you want to use, while the STCs monitor both room and evaporator temperature and relay or cut power only to the light bulb. This way there's no need to mess with the A/C unit in any way, and you can use whatever A/C you want.

I have a small analog GE window unit, 5000 BTUs, the copper temp sensor wire for the AC was connected to the inside facing cooling fins with little plastic snaps and was easily removable, and could be simply moved backwards to the outside portion of the unit, ie, the hot section, wouldn't this trick the sensor into remaining on without the need for a separate 5v lightbulb build or similar heating measure?

I just want the room down to 50-55F, so I'm hoping that a single INKBIRD will be fine without the need for a second to keep the fins from icing up?

 

[LavaAle]

It will do, but you won't have control over the room temp, only over the fins/evaporator temp. Which may be enough though, definitely give it a try!

 

[bembel]

It will do, but you won't have control over the room temp, only over the fins/evaporator temp. Which may be enough though, definitely give it a try!

Sorry I was not clearer, I meant using the single temp controller to turn the AC on/off based on room temp, and that by pushing the copper bulb of the current temp sensor outside where its warm, the AC won't stop cooling when it hits 62F. I just wonder if pushing it beyond 62F to say, 55F, will cause the fins to freeze up.

Not a big deal to add the second controller for the fins, just might not need it.

 

[LavaAle]

Sorry I was not clearer, I meant using the single temp controller to turn the AC on/off based on room temp, and that by pushing the copper bulb of the current temp sensor outside where its warm, the AC won't stop cooling when it hits 62F. I just wonder if pushing it beyond 62F to say, 55F, will cause the fins to freeze up.

Not a big deal to add the second controller for the fins, just might not need it.

My bad. AC evaporators get cold really fast. The beauty of using two controllers (or the coolbot) is that you don't have to worry about the fins freezing, which will happen eventually if you just let it cool beyond the factory minimum, especially the first time.

 

[bembel]

My bad. AC evaporators get cold really fast. The beauty of using two controllers (or the coolbot) is that you don't have to worry about the fins freezing, which will happen eventually if you just let it cool beyond the factory minimum, especially the first time.

Hi I appreciate the advice, time to wire up another Inkbird or wait for my tech buddy to make me an arduino version, if using an arduino set up with smaller thermistors, is it best to attach the thermistor to the coils going into the fins, or attach to the fins themself, or does it not matter?

 

[tvfoodmaps]

Hi, sorry for reviving an old thread but there appears to be a lot of great participants in the thread. I'm thinking of doing something like this (a DIY coolbot). Has anyone turned this info into a project with more detailed instructions. I have experience with some DIY projects with Raspberry Pis and Arduinos but would love to review an already completed project.

More specifically I'm curious if anyone has had their DIY approach running for more than a few months successfully?

The part of the project that seems most concerning is the sensor for the fins, given the temperature. What sensor have you found to work?

 

[chillestbot]

I built a couple and a friend ran one for over 6 months. Apparently it's not working now but I haven't had a chance to fix it for him, so I don't know what the issue is. I suspect a sensor was damaged as I built them with garbage wiring.

The threat of lawsuits from Cool Bot owners had a chilling effect on doing this activity publicly.

 

[tvfoodmaps]

If anyone could comment (or DM me) with info on which sensors and heating elements they have used that would be really appreciated.

 

[kshuler]

Grat project. Is it working well for people? Sorry to resurrect this after months.

 

[wieldling]

Ya, they work great! It's a nice simple design. I'd be curious to learn if anyone has been successful setting them up with those $15 controllers.