Power Supplies
Introduction
Advantages
of a Laboratory Benchtop Power Supply
Commercial
Cooler Power Supply
Match
TEC to Controller's Capability
Match
Power Supply to Controller
Match
Power Supply to TEC
Special
Notes: Using Multiple Power Supplies
General
Information About Power Supplies
Some
Precautions and Warnings
MANUFACTURERS,
DISTRIBUTORS AND RETAILERS
Additional
Notes
Using Multiple Power Supplies in Parallel
| INTRODUCTION |
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We do not recommend specific power supplies unless we are preforming
the design and engineering of the entire project, however, here are some
notes we put together about some power supply sources.
Note: "TEC" stands for Thermoelectric Cooler, which
is a Peltier module.
| ADVANTAGES OF A LABORATORY BENCHTOP
POWER SUPPLY |
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For working with low power TECs we use a TENMA Laboratory DC Power Supply
72-2005. It has over current protection so that it shuts off if the current
goes too high. It also has coarse and fine adjust with meters for the current
and voltage. It is a nice general purpose power supply for up to about
20 vdc and 3 amps. There are other TENMA benchtop power supplies with more
power. These are available from 
Newark
among others.
Your local electronics store may have TENMA or other power supplies.
| COMMERCIAL COOLER POWER SUPPLY |
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If you are working with a commercial TEC based "cooler" (such as Igloo)
it will have its own power supply. You may not be able to find the information
you need, though, on the power supply or TEC. Be careful that you determine
the operating voltage and the Imax (max current draw) and that these values
match your temperature controller's capability.
| MATCH TEC TO CONTROLLER'S CAPABILITY |
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These two examples use a Model 5C7-350 temperature
controller: 12-24 vdc, 7.5 amperes max without additional heatsinking.
Note that the Model 5C7-350, like the Model 5C7-378,
requires at least 12 vdc for its own operation, but can be configured to
use two power sources. For TECs that have a Vmax less than 12 vdc use one
power source for the controller and a second for the low voltage TEC.
EXAMPLE 1:TE
Technologies Peltier Modules
This first one is OK for the 5C7-350. (We use the potted version
of this one in-house.)
#1) TB-127-1.0-1.5 . . . Imax 3.1 amps, Vmax 15.7 vdc
You would need a more powerful controller, such as our Model 5C7-362 for
this next one because of the high Imax.
#2) TB-127-2.0-1.5/48 . . . Imax 12.4 amps, Vmax 15.9
vdc
EXAMPLE 2:Tellurex
Peltier Modules.
(I believe some commercial coolers use these TECs. )
These 3 models are fine for our model 5C7-350 temperature controller
which allows for 7.5 amperes maximum at room temperature. (For #2,
you would need to use two power sources - one for the controller and one
for the TEC.)
#1) CZ1-1.4-127-1.65 . . . Imax 5.6 amps, Vmax 16.1
vdc.
#2) CZ1-1.4-63-1.65 . . . Imax 5.6 amps, Vmax 7.9 vdc.
#3) CZ1-1.0-127-1.27 . . . Imax 3.9 amps, Vmax 16.1 vdc.
You would need a more powerful controller, such as our Model 5C7-362 for
this next one because of the higher Imax. Or, in the case of the 5C7-350
controller, you would need additional heatsinking for the controller.
#4) CZ1-1.4-127-1.14 . . . Imax 8 amps, Vmax 16.1 vdc.
| MATCH POWER SUPPLY TO CONTROLLER |
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Our controllers generally run on 12 to 24 or 12 to 28 vdc. For example,
the Model 5C7-378 runs on 12 to 24 vdc.
Most controllers run the TEC with the same power that is used to run
the controller itself. In this situation a single output power supply
will suffice.
Controllers such as the 5C7-378 and 5C7-350 can also run low voltage
TE modules, but still require 12 to 24 vdc for the controller. In this
case you can use one power supply for the controller and one for the TEC,
or dual output power supply. Usually the power supply for the controller
would be 12 vdc and 1 amp - but the current draw is less than 500 milliamps,
and the Model 5C7-350 can optionally go down to 9 vdc, and so smaller power
supplies or even batteries could be used for the controller itself.
We can and do build controllers that run on 5 vdc or some other custom
voltage or voltage range.
| MATCH POWER SUPPLY TO TEC |
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The power supply must be able to supply the Imax of the TEC. It should
be rated for the TEC's Imax or more.
The power supply must be able to supply "sufficient" voltage. It should
be rated for the TEC's Vmax or less. It may be possible to have optimal
operation of the TEC at 75% of the Vmax. A power supply with an adjustable
voltage may be useful, especially for odd Vmax values such as 4.75 vdc.
If powering the controller and TEC from the same power output, add the
requried milliamps of the controller to the Imax of the TEC to determine
the power supply requirement.
Example:
For a module with these specifications:
Vmax 16.1 vdc
Imax 5.6 amps
We can run this with a controller from one power
supply. If the controller requires 250 milliamps, we should add 0.25 amps
to the Imax and that gives us 5.85 amps maximum.
So then, the power supply we select may be 12
to 16 vdc, with a capacity to handle 5.85 or more amperes.
| SPECIAL NOTES: USING MULTIPLE POWER
SUPPLIES |
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Click to see note below for information
on using multiple power supplies in parallel.
USING MULTIPLE POWER SUPPLIES AND MULTIPLE 5C7-350A CONTROLLERS . .
. It may be possible to connect multiple sets of supply/controller/module
using a 5C7-350A. See the 5C7-350
Implementation Notes.
| GENERAL INFORMATION ABOUT POWER SUPPLIES |
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We buy power supplies on-line and just about any will probably be OK.
We have no particular recommendations, though. We use switching power supplies,
not linear. They are generally lighter, less expensive, hold to the required
voltage better, and dissipate less heat.
You need to multiply the Vmax of the TEC by the Imax to determine minimum
wattage, and then buy a power supply that has the voltage you want and
more than enough wattage. for example the Tellurex CZ1-1.4-127-1.65 has
an Imax 5.6 amps and Vmax 16.1 vdc. You may be able to run a TEC at ¾
Vmax and still get optimal performance, and so I might try a 12
volt power supply. 5.6 amps X 12 vdc = 67.2 watts. So a 12 vdc 75 watt
(or 100 watt) power supply should be OK.
Matching the right power supply (considering economics as well as power)
is an area that requires some research and design experimentation on your
part.
Some power supplies from other manufacturers may be
smaller or
lighter.
Also, usually, the less power you need the smaller the power supply can
be.
Note if they are single or multiple output, also. If you are going to
run fans you may want a multiple output supply that also provides the VDC/AMPS
needed for the fans.
When building a product for process control, note that 24 vdc is considered
by some to be the current "standard" for industrial applications, and so
you may want to consider using 24 vdc for the controller and TEC. If building
a transportable product you may want to use 12 vdc, as provided by an automaobile
battery, for the controller and TEC.
| SOME PRECAUTIONS AND WARNINGS |
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These precautions and warnings should not be used in lieu of
those provided by the controller, TEC and power supply manufacturers.
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Heatsink or Cool if Necessary: Be careful to note the cooling requirements
of the power supply. You may see a power supply that provides the voltage
and amperage you need but then there will be a note to the effect that
the power supply requires certain ambient temperature conditions, or forced
air cooling, or similar.
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Supply Sufficient Amperage: Do not connect an output that sources
less amperage than the the maximum current draw of the devices you are
powering. If powering the controller and TEC add about 0.5 amps (check
with us for the current draw of a specific controller model) to the Imax
of the TEC to determine the maximum current draw you should allow for.
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Supply Sufficient Voltage: Do not use a linear power supply for
the controller unless you are sure it will provide the required voltage
under load. For example, the 5C7-36x series of controllers require 12 vdc
minimum for communications to operate normally.
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Avoid Shorts and Sparks and Miswiring: Always have the supply power
OFF when making or changing connections. Double-check your connections.
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Prevent Thermal Runaway, Note 1: Have a thermometer or other way
to test the TEC to see if the working side is heating when you expect it
to heat, or cooling when you expect it to cool, so that you can be sure
you hooked up the TEC with the appropriate polarity. If the TEC is hooked
up with the wrong polarity you could experience thermal runaway and burn
out the sensor or TEC or attached equipment/devices.
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Prevent Thermal Runaway, Note 2: If your controller has a alarm
settings with "power out shutdown if alarm" use this to prevent your TEC
from thermal runaway.
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| MANUFACTURERS, DISTRIBUTORS
AND RETAILERS |
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We can supply the following Single Output Switching
Power Supplies. Contact us for more information.
Dimensions:
199x110x50mm (5.1"x2.8"x1.3")
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Model S-150-12: 12V, 0~12.5A, $40.50, (±10%
DC adjustment range), 150W.
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Model S-150-24: 24V, 0~6.5A, $40.50, (±10%
DC adjustment range), 150W.
Dimensions:
215x115x50mm (5.5"x3"x1.3")
Model S-320-12: 12V, 0~25A,
$92.25,
(±10% DC adjustment range), 320W.
Model S-320-24: 24V, 0~12.5A, $92.25, (±10%
DC adjustment range), 320W.
Other Suppliers
Some suppliers below were mentioned to me by customers, and others we found
with the
Google
search engine. These are listed in no particular order. You may be able
to find others by using a search engine.
In addition to the companies listed below there are the major parts
distributors such asMOUSER
ELECTRONICS,JAMECO,
andALLIED
ELECTRONICS.
Be sure to discuss your power supply requirements with
the power supply vendors. They can provide the best advice.
Their LPS113 is one example of a power supply that provides
12 vdc and more than 5.6 amps.
http://www.astecpower.com/products/datasheets/lp/lps110revb.pdf
The above is just the first one in the list that I looked at.
I was told by one customer that AstroDyne tends to have the
units in stock and you can get priority shipping.
Ships
within 3 days, and Acopian has been doing so for 40 years.
Industrial Power Quality has been their "exclusive focus for
more than 70 years".
You may have several power supplies that you would like to
use to simultaneously power and control multiple TECs. The power supplies
of a commercial cooler, for instance, are usually meant to supply power
for the one TE module in the cooler - but what if you have several and
want to use their combined power for temperature control.
What if you want to use one temperature controller with multiple TE
modules using multiple power supplies?
The following discussion assumes that all power supplies are the same
model/manufacturer with the same ratings of voltage and maximum amperage
for the VDC outputs, and it assumes that all the TE modules are meant to
be used with those power supplies.
You could purchase a new power supply that will handle the required
load, or you may be able to connect multiple power supplies from the coolers
in parallel.
Some power supplies can be connected in a similar manner as batteries
- in series or parallel. Connecting each power supply's (+) to the (+)
of one or more additional power supplies, and similarly the (-) to the
(-), results in no change in the voltage but an increase in the available
amount of amperage. You would have to ask the power supply manufacturer
if the type of power supply, and the number of power supplies, you want
to connect together can be connected in parallel. CAUTION: Do not connect
power supplies in series or parallel unless you know for certain they are
capable of being connected and used in such a configuration safely!
If they can be connected in parallel, you could use one controller with
multiple power supplies that are connected in parallel. CAUTION: Be
sure the temperature controller is rated for the total Imax amperage (maximum
current draw) of all the TE modules being powered.
