A Salinometer built for the Science Olympiad

This is a Digital Salinometer which [Daniel Kramnik] built as a Science Olympiad entry. He’s a Junior in High School and when looking for a project to enter into the Water Quality event he was interested in achieving greater accuracy than a mechanical hydrometer provides.

We think the circuit design is very impressive for anyone who hasn’t complete formal training as an engineer, and outstanding for someone as young as [Daniel]. Measurements depend on two main parts, a temperature control and a salinity sensor. These are both necessary because fluctuation in sample temperature will affect the salinity reading.

A Peltier element is used to heat the water sample if it doesn’t fall within a set range of temperatures. From there, an Op-Amp circuit conditions a signal running through the sample, passing an output to the ADC converter chip which drives the three-digit readout. [Daniel] calculates an accuracy within 0.0014%. He must be on the mark because he’s won his regional competition and will soon compete at the state level.

Two ways to convert an electric cooler to a humidor

It’s not a proper humidor in the technical sense (there isn’t any specific way to moderate the humidity) but [Dzzie] came up with a couple of ways to keep his cigars cool in the summer heat.

Both versions use a Coleman electric cooler as the enclosure. This hardware uses a Peltier device to keep it cool inside. The first attempt at use a thermostat with this worked by adding an external relay to switch mains power. A thermostat dial hangs out inside the cooler to give feedback to the relay board. This worked, but it’s a really roundabout approach since the cooler operates on 12V, and this method uses a mains-to-12V adapter. If [Dzzie] decides to hit the road the relay won’t work when the cooler is powered from a 12V cigarette lighter in the car.

The second rendition fixes that issue. He moved to a 12V relay, and used a car cellphone charger to supply the 5V of regulated power his control circuitry needs to operate.

Peltier powered sous-vide rig gets it right every time


It seems that sous-vide cooking is becoming increasingly popular lately. [Meseta] caught the sous-vide bug and wanted to try his hand at it, though he did not have enough money for a premade sous-vide cooker. After seeing a good handful of lackluster DIY sous-vide rigs online, he decided that he would design and build a sous-vide cooker of his own.

He already had a Forebrain microcontroller at his disposal to use as a PID controller, but what he really needed was a cooking vessel. Rather than use an old crock pot or similar device, he purchased a small personal refrigerator that could be used for cooling or heating. The unit ran off a Peltier cooler that could be switched between modes, making it quite easy for him to control.

In his blog, he discusses the modification from beginning to end, and even shows off the results of his cooking endeavors. He hasn’t posted code as of yet, but he says that he is more than happy to share it with anyone who might be interested in building their own sous-vide cooker.

Poor man’s Peltier air conditioner

It’s summer in Germany, and [Valentin’s] room was getting hotter than he could handle. Tired of suffering through the heat, and with his always-on PC not helping matters any, he decided that he must do something to supplement his home’s air conditioner. The result of his labor is the single room poor man’s A/C unit you see above.

He had a spare Peltier cooler sitting around, so he put it to good use as the basis for his air conditioning unit. He sandwiched it between a pair of CPU heatsinks before cramming his makeshift heat pump into a shoe box. Warm air is drawn into the box and across the cold side of the Peltier before being blown back into the room. On the hot side of the box air is also pulled in by a fan, drawing heat away from the unit before being exhausted outdoors through his window.

While he hasn’t quantified the machine’s cooling power, he seems quite happy with the results. We have a spare Peltier kicking around here somewhere, perhaps we should try building one just for grins.

Chill your phone for longer battery life?

The first specs we look at when choosing a cellphone are the battery life numbers. We know that eventually we’re going to see performance loss, and [Dr. West] wanted to see if there’s a way to delay the inevitable. What he found is that ambient temperature affects the battery throughout its life. He set out to build a phone chiller to slow the degradation of the battery.

The research that he points to shows that at room temperature, a Lithium battery will lose 20% of its capacity each year. This seems like a dubious number so do share links to studies that state otherwise in the comments. Whether that 20% is right or not, the point is that cooling the battery will preserve it. With that in mind, [Dr. West] put together a pod that uses a peltier cooler and a heat sink to host his Blackberry while he sleeps. He figures he can reduce the capacity lost per year from 20% down to 14%. This of course comes at the expense of running that cooler every night (in addition to charging the phone when it needs it). But perhaps this solution will spark an idea that leads to a better one.

Peltier cooler based cloud chamber

[Rich] shares with us his build of a Peltier cooler based cloud chamber. This nifty little tool allows him to see the paths that radioactive particles take through alcohol vapor. The system he has come up with is fairly cheap at roughly $100. He’s using Peltier coolers from computers and a cheap ATX power supply. You can see a more detailed instructable here.

[via Make]

Generate electricity with a candle

What you see above is a generator that converts heat to electricity. [Reukpower’s] thermoelectric lamp is one of those hacks that makes you scratch your head even though you understand why it should work. The heart of the system uses a Peltier cool, just like the thermoelectric solar generator. When there is a temperature differential from one side of the Peltier to the other a small current is generated.

In this case a candle heats one side and a heat sink cools the other. The tiny voltage picked up from the Peltier’s contacts is then boosted using a joule thief. We’ve seen LEDs powered with a joule thief before, benefiting from their own low power consumption. In this case, the boost circuit is scavenged from an emergency phone charger and probably achieves higher efficiency than if he had built it himself.