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Aspen Universal Condensate Pump

Universal Peristaltic Condensate Pump
Universal Peristaltic Condensate Pump

Here’s another piece of commercial gear, from an industrial air conditioning unit. These pumps are used to drain the condensate from the evaporator unit, so water doesn’t end up raining down from the ceiling.

Pump Head
Pump Head

This is a peristaltic pump, with a silicone hose forming the pumping element.

Rear Panel
Rear Panel

The test switch & electrical connections are on the back, along with the data label.

Power & Sensor Socket
Power & Sensor Socket

The electrical connections are all on a single 5-pin socket. Along with 240v AC mains, there are a pair of thermistors connected to the unit, which switch the pump on when a 5°C temperature difference across the evaporator coil is detected. When air is cooled, it’s capacity for moisture drops, so the water condenses out on the coil.

Roller Wheel
Roller Wheel

Here the front cover has been removed from the pump, showing the silicone tube & roller wheel. The wheel was originally Cadmium-plated, but exposure to the elements has oxidized this into highly toxic Cadmium Oxide.

Pump Rollers
Pump Rollers

Here you can see the rollers. These pinch the tube at the inlet, and the rotation carries a slug of liquid through the tube to the outlet side.

Pump Tube
Pump Tube

Here’s the tube itself, the main wearing part of the pump. This is replaceable as a spare part.

Motor & Gearbox
Motor & Gearbox

Inside the casing is a shaded-pole motor, connected to a large gearbox, to give the slow rotation for the pump head. The rated speed is 51RPM.

Control PCB
Control PCB

There’s not much to the control PCB. The large resistor forms a voltage dropper, to reduce the mains 240v to a more suitable level for the logic. There’s a TL062C Low-Power JFET Op-Amp & a CD4060BCM 14-stage binary ripple counter forming the logic. The set point is adjustable via the potentiometer.

Pump Triac
Pump Triac

The pump motor is switched via this Z7M SMD triac, not much switching power is needed here as the motor is only a very small shaded-pole type.

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15v Bipolar Supply Testing

Here’s some testing of the first bipolar supply for the Rigol scope. This is the +/-7.5v supply.

Bipolar Supply
Bipolar Supply

Above is the supply built with it’s output filtering. The modules used are a PTN78020W for the positive rail & a PTN78060A for the negative rail.

Under a 1A load across the total 15v output, here’s some scope traces of the ripple on the supply:

+7.5v Rail
+7.5v Rail

Here’s the ripple on the +7.5v rail of the supply, there’s about 75mV of total ripple.

-7.5v Rail
-7.5v Rail

And here’s the -7.5v rail, the ripple on this is slightly lower, at about 50mV. This should be more than satisfactory as the scope has onboard linear regulation after the switching supply.

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13.8v SMPS PSU Build

A while ago I blogged about modifying the output voltage of some surplus Cisco switch power supplies to operate at 13.8v.

Since I was able to score a nice Hammond 1598DSGYPBK ABS project box on eBay, I’ve built one of the supplies into a nice bench unit.

Hammond ABS Case
Hammond ABS Case
Supply Unit
Supply Unit

Above is the supply mounted into the box, I had to slightly trim one edge of the PCB to make everything fit, as it was just a couple of mm too wide. Luckily on the mains side of the board is some space without any copper tracks.

PSU Fan
PSU Fan

These supplies are very high quality & very efficient, however they came from equipment that was force-air cooled. Running the PSU in this box with no cooling resulted in overheating. Because of this I have added a small 12v fan to move some air through the case. The unit runs much cooler now. To allow the air to flow straight through the case, I drilled a row of holes under the front edge as vents.

Output Side
Output Side

Here is the output side of the supply, it uses standard banana jacks for the terminals. I have used crimp terminals here, but they are soldered on instead of crimped to allow for higher current draw. The negative return side of the output is mains earth referenced.

I have tried to measure output ripple on this supply, but with my 10X scope probe, and the scope set to 5mV/Div, the trace barely moves. The output is a very nice & stable DC.

This supply is now running my main radio in the shack, and is small enough to be easily portable when I move my station.