Motech LPS-300 series

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Motech LPS-300 series
Motech LPS-301 logo.png
Status supported
Source code motech-lps-30x
Channels 1/3
Voltage/current (CH1) 0-30 V / 0-3 A, model-dependant
Voltage/current (CH2) 0-30 V / 0-3 A, model-dependant
Voltage/current (CH3) 3.3/5 V / 0-3 A, model-dependant
Connectivity RS232
Features output on/off, calibration

The Motech LPS-300 series of programmable power supplies consists of five 1-channel or 3-channel devices with optional RS232 connectivity.

The devices were also sold as Amrel LPS-301 to LPS-305 by American Reliance and partly under further brands, e.g. the LPS-305 as Tecpel TPS-3025.


The models differ only in the number of available channels, maximum voltage and maximum current output:

Model Power output Channels Voltage/current sigrok status
LPS-301 30 W 1 30 V/1 A or 15 V/2 A Supported
LPS-302 60 W 1 30 V/2 A or 15 V/4 A Planned
LPS-303 90 W 1 30 V/3 A Planned
LPS-304 70 W 3 ±30 V/1 A or ±15 V/2 A; 5 V/2 A Planned
LPS-305 165 W 3 ±30 V/2.5 A; 3.3 or 5 V/3 A Planned

The three-channel versions have the two main channels wired together for symmetric power supply, but the voltages can be set independantly, if desired. They can be set on or off only together.

The planned models are prepared in the driver motech-lps-30x and can be implemented easily as soon as devices for testing get available.

These specifications are common to all models:

30 V channels
Voltage Current
Programming resolution 10 mV 1 mA
Programming accuracy 0.05% + 20 mV 0.15% + 5 mA
Readback accuracy 0.1% + 20 mV 0.2% + 5 mA
Ripple (10 Hz to 20 MHz) 1 mV rms / 10 mV p-p 10 mA rms
Load regulation 0.001% + 1mV 0.01% + 1mA

These specifications apply only to models having a 3.3V/5V output:

3.3/5 V channel
Voltage Current
Ripple (10Hz to 20MHz) 2 mVrms / 10mVp-p 10mArms
Load regulation 0.001% + 1mV 0.01% + 1mA

The devices can be calibrated easily requiring nothing but a multimeter of sufficient precision.


The communication with the device is via an optional RS-232 port (Option 02). The port parameters are 2400 Baud, 8n1.

All commands are plain ASCII. All commands are terminated by \r, \n or \r\n. Another command sent before reception of the reply (usually OK) will be ignored. It seems that trailing digits for numerical parameters can be omitted.

Command Reply Description
BEEP(0|1|2|3) OK Beeper function 0: disable; 1: enable; 2: force alarm (beeper test) 3: end force alarm.
CALI(0|1|2)  ? Calibration 0=end; 1=begin; 2=input parameter
There seem to be no plausibility checks and the description is incomplete. Messing around with the calibration is strictly discouraged and can cause odd behaviour!
HELP (see right) OK Output list of commands (several lines)
IOUT(n) d.dddd OK Current readback
ISET(n) d.dddd OK Set output current
LOWA(0|1) OK CC output compensated 0=off; 1=on (what does this setting do?)
MODEL \r\nLPS-␣␣␣␣ OK Get model number (reply contains spaces instead of model no in FW 1.17, seems to be a bug)
OUT(0|1) OK Disable/enable output. OUT without a parameter seems to disable it.
STATUS <decimal> OK Working status, bitwise encoding.
Bit 0, channel 1 mode: 0: CV 1: CC.
Bit 1, channel 2 mode: 0: CV 1: CC.
Bit 3,2, tracking: 00: independant; 10: to channel 1; 11: to channel 2.
Bit 4, digital output 3: 0: off; 1: on.
Bit 5, digital output voltage: 0: 5 V; 1: 3.3 V.
Bit 6, output 1/2: off; 1: on.
Bit 7, output 3: 0: ok; 1: overloaded.
Bit 8, Fan: 0: off/low; 1: on/high
Bit 9, beeper: 0: disabled; 1: enabled. Corresponds to BEEP0/1.
Bit 10, CC output compensated: 0: off; 1: on
TRACK(0|1|2) OK Tracking 0=independant; 1=from channel 1; 2=from channel 2. Tracking seems to mean that channels 1 and 2 are synchronous on multi-channel models.
VDD(0|3|5) OK Set ("digital") output 3 0=off; 1=3.3 V; 5=5 V
VERSION \r\nVer-1.17␣\r\n OK Get version number.
Bug: Seems not to work while the output is active on LPS-301 1.17, no reply!
VOUT(1|2) dd.ddd OK Voltage readback
VSET(1|2) dd.ddd OK Set output voltage. Entering more than 3 post-dot digits will overwrite starting from the left!
The specified resolution is 10 mV. However, the actual resolution seems to be slightly higher, possibly due to rounding during decimal to binary conversion or depending on calibration.
* \r\nERROR\r\n OK Error (invalid command).

OK means \r\nOK\r\n.


Function Target Parameters Comment
SR_CONF_OUTPUT_CHANNEL Device Track1 | Track2 In tracking mode the other main channel seems to follow the tracked channel.
SR_CONF_OUTPUT_VOLTAGE Channel Double 0-30.0 Get: Query output voltage. Updated only if sampling is active! Channel 3 allows only 5 V or 3.3 and 5 V, depending on model!
SR_CONF_OUTPUT_VOLTAGE_MAX Channel Double 0-30.0 Get: Get max. possible voltage. Set: Set output voltage. Channel 3 allows only 5 V or 3.3 and 5 V, depending on model!
SR_CONF_OUTPUT_CURRENT Channel Double 0.005-x.xxxx Get: Query output current. Updated only if sampling is active! Channel 1 and 2 only, channel 3 is fixed!
SR_CONF_OUTPUT_CURRENT_MAX Channel Double 0.005-x.xxxx Get: Get max. possible current. Set: Set output current. Channel 1 and 2 only, channel 3 is fixed!
SR_CONF_OUTPUT_ENABLED Channel Boolean on/off Switch output on or off. Channels 1 and 2 are connected, accessing one will also set the other one.

Additionally sampling commands are possible.