This will be my weekend project but before I tear into it, I wonder if anyone has any experience with these or knows of a schematic? This is the third one I've had. First one quit cooling, the second one and this one stopped heating. Given my experience with failure rate, these things seem poorly designed.
I am guessing it contains Peltier module and if that is true, I suspect the module may be dead or the drive circuity may be the culprit. Any insight from anyone having experience with this is appreciated. J
Good point - yes bad implementation of a design. (like having a cheap fan b low across the Peltier (if it uses one) or, badly implemented airflow passa ges after all the components were shoe-horned into the package.)
Did not keep the old ones - both were warranty replacements with a $25 surc harge for replacement. I figured it was worth the $ and not my time. Now, since this one went belly up (and there seems to be a lot of similar failu res posted in user feedback) I figure I need to get in and *really* fix thi s thing - if my spouse wasn't so enamored with it, I'd dig out the 15 yo Sa lton one to use.
Following up on my repair effort, I'll document what I found in case anyone going down this road stumbles on this writeup.
In short the unit uses a Peltier module heat pump to both heat and cool the yogurt container. The Peltier module was bad in my unit - gave a constant ~30K ohms reading, connected it to a 12vdc battery source, no heat what so ever. The module is a TEC1-12705. To my surprise none of the usual electron parts houses have them (Mouser, D igikey, avnet, allied, newark, etc.) Amazon has them ranging in price from $6 to $10 from varying sources and from what I see in the reviews, all par ts are of questionable quality. To my surprise, they are available through Walmart! Not sure where to get the OEM part - suggestions? pointers appreciated.
Description of the unit, it contains:
1) 5 VDC 6A smps, which feeds a...
2) a 2"x3" micro based control module that contains connections for: the Pe ltier module, a rtd/thermister temp sensor, power supply input.
3) the heat/cool stack composed of 1.25" aluminum heat block encased in sty rofoam, the peltier module, a massive Al finned heatsink (5"x 2.5") and a 3 " fan bolted to the finned heatsink.
Getting the unit apart is a little tricky because it has 4 plastic fingers that lock the bottom half of the unit to the top half - need to simultaneou sly unlock all four tabs then separate the top and bottom.
Couldn't see any obvious design or implementation screwups, although I ques tion why there is a 1.25" thick piece of aluminum between the Peltier modul e and the bottom of the yogurt container. I'll need to do some heat transfe r calcs to see if they are controlling the module correctly and take some t emp measurements to infer their desired (required) heating and cooling temp s.
From what I could tell on the scope the output to the Peltier module was fa irly smooth DC voltage that is (my guess) a LPF PWM output to a power tran sistor (MOSFET?) from the microcontroller The markings on the chip were un readable due to some clear coat that was put on the chip. A lot of specula tion here since I could not read a lot of the component markings. My google fu failed to turn up anything about the components, although the PS looks l ike it is an off the shelf module from somewhere.
Next step is to get the replacement Peltier module, perhaps upgrade the the rmal silicon grease, and reassemble. J
he yogurt container. The Peltier module was bad in my unit - gave a consta nt ~30K ohms reading, connected it to a 12vdc battery source, no heat what so ever.
Digikey, avnet, allied, newark, etc.) Amazon has them ranging in price fr om $6 to $10 from varying sources and from what I see in the reviews, all p arts are of questionable quality. To my surprise, they are available throu gh Walmart!
Walmart is a poor man's Amazon. Many of the things sold on Walmart's onlin e site are deliverd from someone's basement, and I don't know if Walmart wo uld offer the same protections as Amazon, as good or as bad as that might b e.
On Sunday, April 19, 2020 at 4:43:08 PM UTC-4, snipped-for-privacy@gmail.com wrote:
ne going down this road stumbles on this writeup.
he yogurt container. The Peltier module was bad in my unit - gave a consta nt ~30K ohms reading, connected it to a 12vdc battery source, no heat what so ever.
Digikey, avnet, allied, newark, etc.) Amazon has them ranging in price fr om $6 to $10 from varying sources and from what I see in the reviews, all p arts are of questionable quality. To my surprise, they are available throu gh Walmart!
Peltier module, a rtd/thermister temp sensor, power supply input.
tyrofoam, the peltier module, a massive Al finned heatsink (5"x 2.5") and a 3" fan bolted to the finned heatsink.
s that lock the bottom half of the unit to the top half - need to simultane ously unlock all four tabs then separate the top and bottom.
estion why there is a 1.25" thick piece of aluminum between the Peltier mod ule and the bottom of the yogurt container. I'll need to do some heat trans fer calcs to see if they are controlling the module correctly and take some temp measurements to infer their desired (required) heating and cooling te mps.
fairly smooth DC voltage that is (my guess) a LPF PWM output to a power tr ansistor (MOSFET?) from the microcontroller The markings on the chip were unreadable due to some clear coat that was put on the chip. A lot of specu lation here since I could not read a lot of the component markings. My goog lefu failed to turn up anything about the components, although the PS looks like it is an off the shelf module from somewhere.
hermal silicon grease, and reassemble.
Last follow-up on my repair. The Peltier module I got from Amazon seller did not conform to the general rule that the 'hot side' is the side that has the p/n printed on it. Mine was opposite, which I did not find out until I had the unit reassembled and tried it. The module broke when I tried to remove it - the thermal grease made it very difficult to remove. Ordered a second module. When I got the replacement, I tried it before putting the thermal grease on it and assembling it. I connected the red wire of the Peltier module to the '+V out' on the contr oller board, and the black wire of the module to the '-V out' on the contro ller. Powered up the unit and started a cycle. The first thing that is su ppose to happen is a heating phase (default time of 8 hrs but is configurab le) followed by a cooling phase. I started a cycle, felt the module for th e heat side, and then mounted that head side against the thermal plate on t he 'container side' of the unit. The voltage sent to the Peltier module is 12 VDC. A quick check of the control module is to start a cycle and measu re the voltage. at the +Vout and -Vout pins. Once the heating/cooling side was determined, I reassembled the unit. A wor d of caution: the massive heat sink in the 'bottom half' of the unit is hel d in by four machine screws. ( this heat sink comes into play when the unit goes to a cooling phase and changes polarity on the Peltier module). The machine screws had silicon rubber spread on top of them, presumably to deter any repair. You will have to scrape it out of the fillips screw head s to get a bite with a screw driver. Once out, the rest can be removed wit h a wire brush. The heat sink has rubber spacers on each end of the heat sink. Do not remov e these. When reassembling, do not overtighten the screws when installing the heat sink. Try to remember how 'loose' they were when you removed them and tighten them to about the same level. I made mine snug to the point t hat there was just a little resistance from the rubber spacers. If the scr ews are overtightened, it could crack/damage the module. A good application of thermal grease here is important.
I got the replacements from seller on Amazon and prices range from ~$2/part to ~12/part. Comments for any of the parts ranged from good to junk...no matter what the price. I paid $6. I called Laird who makes TEC modules an d they have a cross that sells for $32 at mouser. I decided to try the $6 p art and see what happens. If it dies, I may go for the expensive one but Cuisenart will replace the unit for $25+10 ship so it probably isn't worth the effort and cost. YMMV. I didn't see any obvious design or implementation flubs (that I could easil y correct). I do question why the metal block to the yogurt well was over
yone going down this road stumbles on this writeup.
the yogurt container. The Peltier module was bad in my unit - gave a const ant ~30K ohms reading, connected it to a 12vdc battery source, no heat what so ever.
r, Digikey, avnet, allied, newark, etc.) Amazon has them ranging in price f rom $6 to $10 from varying sources and from what I see in the reviews, all parts are of questionable quality. To my surprise, they are available throu gh Walmart!
e Peltier module, a rtd/thermister temp sensor, power supply input.
styrofoam, the peltier module, a massive Al finned heatsink (5"x 2.5") and a 3" fan bolted to the finned heatsink.
ers that lock the bottom half of the unit to the top half - need to simulta neously unlock all four tabs then separate the top and bottom.
question why there is a 1.25" thick piece of aluminum between the Peltier m odule and the bottom of the yogurt container. I'll need to do some heat tra nsfer calcs to see if they are controlling the module correctly and take so me temp measurements to infer their desired (required) heating and cooling temps.
s fairly smooth DC voltage that is (my guess) a LPF PWM output to a power t ransistor (MOSFET?) from the microcontroller The markings on the chip were unreadable due to some clear coat that was put on the chip. A lot of specul ation here since I could not read a lot of the component markings. My googl efu failed to turn up anything about the components, although the PS looks like it is an off the shelf module from somewhere.
thermal silicon grease, and reassemble.
l rule that the 'hot side' is the side that has the p/n printed on it. Mine was opposite, which I did not find out until I had the unit reassembled an d tried it. The module broke when I tried to remove it - the thermal grease made it very difficult to remove. Ordered a second module.
on it and assembling it.
troller board, and the black wire of the module to the '-V out' on the cont roller. Powered up the unit and started a cycle. The first thing that is su ppose to happen is a heating phase (default time of 8 hrs but is configurab le) followed by a cooling phase. I started a cycle, felt the module for the heat side, and then mounted that head side against the thermal plate on th e 'container side' of the unit. The voltage sent to the Peltier module is 1
2 VDC. A quick check of the control module is to start a cycle and measure the voltage. at the +Vout and -Vout pins.
ord of caution: the massive heat sink in the 'bottom half' of the unit is h eld in by four machine screws. ( this heat sink comes into play when the un it goes to a cooling phase and changes polarity on the Peltier module).
o deter any repair. You will have to scrape it out of the fillips screw hea ds to get a bite with a screw driver. Once out, the rest can be removed wit h a wire brush.
ove these. When reassembling, do not overtighten the screws when installing the heat sink. Try to remember how 'loose' they were when you removed them and tighten them to about the same level. I made mine snug to the point th at there was just a little resistance from the rubber spacers. If the screw s are overtightened, it could crack/damage the module. A good application o f thermal grease here is important.
rt to ~12/part. Comments for any of the parts ranged from good to junk...no matter what the price. I paid $6. I called Laird who makes TEC modules and they have a cross that sells for $32 at mouser. I decided to try the $6 pa rt and see what happens. If it dies, I may go for the expensive one but Cui senart will replace the unit for $25+10 ship so it probably isn't worth the effort and cost. YMMV.
ily correct). I do question why the metal block to the yogurt well was over 1 inch long.
Very helpful - to clarify - was your repair successful, and is it still run ning? What is the Cuisinart replacement? The whole yogurt maker? or just th e TEC?
umm, sorry, dont quite understand your question. Are you asking what the component is that is marked as Q2 on the PCB? If so, sorry, no clue. My unit is assembled and I don't want to take it apart. I suggest you try to determine the traces to/from the component, take some voltage measurements on its terminals and make a reasonable guess for a replacement. It the component in question drives the TEC, any generic power transistor should suffice. You should be able to determine the power rating of the component from its packaging. If you find a schematic, please post a link to it. Good luck J
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