Daihatsu MDP-REV-D Speed Switch Unit 24VDC
Daihatsu
New product
The Daihatsu MDP-REV-D Speed Switch Unit is a digital engine-speed monitoring and protection device used in marine diesel generators and auxiliary-engine control systems.
Daihatsu’s instruction manual describes the Speed Switch Unit-D as a revolution detector with a digital display function, designed to provide accurate RPM measurement and multiple programmable speed-detection outputs for engine control and protection.
The genuine Daihatsu packaging shown here identifies the unit as:
Product: ASSY: SPEED SWITCH UNIT-D DC24V
Model / Family: MDP-REV-D
Daihatsu Reference: 00853-001
Additional Reference: 7835149
Drawing / Code: FD-02-406
Manufacturer: DAIHATSU DIESEL MFG. CO., LTD.
Country: Japan
The front display is marked:
SPEED SWITCH
MDP-REV
#12
#13
#14
#14L
with setting keys:
F
▲
▼
S
The MDP-REV-D is a digital speed relay / revolution detector / RPM switch used to monitor engine rotational speed and provide contact outputs at programmed speed thresholds.
Daihatsu’s manual states that the unit combines:
in one compact device.
For this reason, buyers may search for the same part under many different names:
Speed Switch
Speed Relay
RPM Relay
Revolution Detector
RPM Detector
Overspeed Relay
Speed Measuring Unit
Engine Speed Monitor
All of these are relevant buyer-search phrases for MDP-REV-D.
The MDP-REV family is also documented by Meiyo Electric Co., Ltd.
Meiyo Electric’s official current product page lists MDP-REV as a digital speed relay and provides detailed specifications including 24VDC power supply, digital display, 4–20mA output and multiple contact outputs.
Marine-market listings also commonly describe the product as:
Daihatsu / Meiyo Electric MDP-REV-D Speed Switch
which is an important additional keyword for sourcing.
Unlike older analogue speed relays, MDP-REV uses a digital display.
The official Meiyo specification gives:
Maximum display digits: 4
Display type: Red 7-segment LED
and allows speed values to be digitally programmed.
The Daihatsu manual also describes digital speed indication up to four digits.
This provides easier setup and better readability than fixed analogue relay settings.
The front panel contains three primary speed-detection channels:
#12
#13
#14
The instruction manual states that the unit provides three-point revolution detection.
Depending on the specific engine configuration, these programmable points may be assigned to functions such as:
overspeed
speed-dependent interlock
alarm / control threshold
engine sequence logic
The exact meaning of #12, #13 and #14 must follow the specific engine control drawing.
They should not be assumed to perform the same function on every Daihatsu engine installation.
The manual identifies #14L as a dedicated start-up interlock contact.
This is an important feature of the MDP-REV-D.
A start-up interlock can be used in engine-control logic to verify that the engine speed is within the required condition before another control step occurs.
Again, the exact switching logic depends on the engine control system.
One of the most important marine applications of MDP-REV is diesel generator overspeed protection.
Marine engineering references describe the Daihatsu MDP-REV as a Speed Relay / Speed Switch / Speed Measuring Unit used to detect engine RPM from a pickup sensor installed near the diesel-generator flywheel.
When the programmed overspeed threshold is reached, the relevant contact can be used by the engine protection system to initiate shutdown or alarm logic.
This makes the following search phrases especially strong:
Daihatsu Overspeed Relay
MDP-REV Overspeed Switch
Generator Overspeed Protection Relay
Daihatsu RPM Protection Relay
The MDP-REV-D manual contains a dedicated section for connection to the pulse sensor.
In practical marine generator installations, engine speed is commonly detected by a pickup sensor reading rotational pulses from a flywheel or gear.
The speed switch then converts this pulse frequency into displayed engine RPM and switching outputs.
For correct operation, the following parameters must match:
Pickup sensor type
Number of pulses per revolution
gear ratio
programmed engine RPM range
Incorrect settings can result in inaccurate RPM indication and incorrect speed-switch operation.
The MDP-REV provides a 4–20mA analogue output.
Both the Daihatsu manual and Meiyo Electric official specification confirm this function.
This signal can be used by compatible:
engine monitoring systems
remote RPM indicators
automation systems
data acquisition equipment
The official Meiyo specification lists a maximum analogue-output load of 500Ω.
Another important MDP-REV function is a revolution-frequency / pulse output.
The Daihatsu manual identifies a revolution-speed frequency output of approximately:
1 Hz per revolution
and Meiyo’s current specification similarly documents a pulse/frequency output related to shaft revolution.
This can be useful for feeding speed information to other shipboard systems.
According to Meiyo Electric’s official MDP-REV specification:
| Parameter | Specification |
|---|---|
| Power Supply | 24VDC ±25% |
| Power Consumption | Max. 2.7W |
| Measurement Resolution | 0.05% ±1 digit at full scale |
| Detection Resolution | 0.05% ±1 digit |
| Display | 4-digit red 7-segment LED |
| Analogue Output | 4–20mA |
| Contact Outputs | 5 points |
| Contact Response | Under 0.3 sec |
| Operating Temperature | -10°C to +70°C |
| Storage Temperature | -20°C to +65°C |
| Humidity | Below 95%, non-condensing |
| Weight | Approx. 0.2kg |
The genuine packaged MDP-REV-D variant shown here is specifically labelled DC24V.
A current marine-market listing for Daihatsu MDP-REVD provides additional commonly searched configuration details:
Source: 24VDC
Power: 3.2W
Hysteresis: 3.0% at set point
Full Scale: 150 × 10 min⁻¹
Reduction Gear Ratio: 2
Pulse: 75
Analog Output: 4–20mA
These values are useful as buyer/search references but should be checked against the exact engine installation before programming a replacement unit.
The Daihatsu manual describes programmable revolution detection over a broad range.
The manual excerpt specifies standard detection around:
100–9990 min⁻¹
with a separate low-speed range associated with #14L.
Meiyo’s current MDP-REV documentation also supports operation up to 9990 in RPM-based settings.
This wide programmable range allows the same basic speed switch design to be used across different Daihatsu engine installations.
The MDP-REV-D manual documents programmable or defined hysteresis for switching points.
A commonly listed default is:
3.0%
for the MDP-REV-D configuration.
Hysteresis prevents the output relay from repeatedly switching on and off when engine speed is fluctuating very close to the set point.
A documented Daihatsu 8DK-20E auxiliary engine parts reference lists:
S102 – Speed Switch Unit Assembly
Type: MDP-REV D
24V DC
3.2W
Part reference: AQA10009590
This establishes a direct documented application of MDP-REV-D in Daihatsu marine generator machinery.
For SEO, these are valuable related search phrases:
Daihatsu 8DK-20E MDP-REV-D
8DK-20E Speed Switch Unit
AQA10009590 Speed Switch
However, AQA10009590 should not automatically be treated as the same ordering number as 00853-001 / 7835149 without checking the engine parts list.
A Daihatsu DC-32 engine operation-manual package also includes a dedicated Speed Switch Unit MDP-REV-D manual.
This supports the MDP-REV-D’s broader use across Daihatsu marine diesel-engine systems.
It also confirms that the speed switch is considered an integrated engine-control/protection component rather than a generic industrial relay.
Marine electrical engineers often encounter MDP-REV on Daihatsu generator engines during class or inspection testing.
A technical reference using a Daihatsu 6DE-18 example explains that the MDP-REV can be used to test overspeed protection by temporarily adjusting the overspeed threshold under controlled test conditions.
This demonstrates why MDP-REV is widely searched not only as a “speed switch” but also as:
overspeed relay
speed measuring unit
RPM relay
engine protection relay
First verify the 24VDC supply at the unit.
Check:
power wiring
terminal block
fuse / upstream protection
grounding
connector condition
The official unit requires nominal 24VDC.
If correct power is present but no display appears, the unit may require internal diagnosis.
Check the pulse / pickup sensor first.
Inspect:
sensor gap
sensor cable
connector
pulse signal
gear/flywheel target
programmed pulse number
The Daihatsu manual specifically covers pulse-sensor connection.
Verify:
pulse setting
gear ratio
full-scale / RPM range
sensor frequency
engine actual RPM
A correct MDP-REV can still show the wrong speed if the pulse or reduction-ratio parameters are entered incorrectly.
Check:
setpoint value
hysteresis
actual RPM
contact wiring
output contact condition
Do not assume the relay output has failed until the programmed threshold has been verified.
The MDP-REV may only provide the overspeed contact—the actual shutdown sequence can also involve:
engine safety relay
fuel shutoff solenoid
engine control panel logic
emergency stop circuit
Test the complete protection chain rather than replacing the speed switch immediately.
Check the analogue-output wiring and receiving-device load.
The official MDP-REV specification states a 4–20mA output with maximum load around 500Ω.
Inspect the #14L setpoint and associated external wiring.
The manual identifies #14L as the start-up interlock contact.
Before replacing a Daihatsu MDP-REV-D, compare:
Model: MDP-REV-D / MDP-REV
Supply: DC24V
Daihatsu Part Reference
Engine Model
Pulse setting
Reduction gear ratio
Full-scale RPM
#12 / #13 / #14 setpoints
#14L setting
Hysteresis
Analogue output configuration
Connector / terminal arrangement
A physically identical unit may still require programming before installation.
The genuine Daihatsu packaging shown here gives two important search references:
00853-001
and
7835149
These should be included when requesting an exact unit because buyers may search by either the assembly description or Daihatsu internal reference.
SEO variants should include:
00853001
00853 001
7835149
Daihatsu 00853-001
Daihatsu 7835149
The genuine packaging also contains:
FD-02-406
This is another useful identification/search reference.
It should be retained in quotations and RFQs, but it should not automatically be interpreted as the primary part number unless supported by the corresponding Daihatsu parts list.
SM MARINE SERVICE™ supports worldwide sourcing and supply of Daihatsu MDP-REV-D Speed Switch Units, RPM detectors, engine protection relays and marine diesel-generator automation spare parts.
Depending on current availability, equipment may be supplied as:
New / Genuine New
New Old Stock
Used Tested Working
Refurbished
Reconditioned
For accurate matching, customers should provide:
Engine Model
Speed Switch Model
Daihatsu Part Number
Full-scale RPM setting
Pulse number
Gear ratio
Existing parameter values
Front/rear photographs
Required quantity
For marine engine automation and Daihatsu spare parts, visit SM MARINE SERVICE™ at www.smmarineservice.com.
Many Daihatsu auxiliary engines and generator engines remain in active service for many years.
The MDP-REV-D provides reliable speed detection, overspeed protection and engine-sequence signals without requiring a complete modern control-system retrofit.
Replacing the exact speed switch can therefore be much more practical than redesigning the entire generator-protection system.
Current marine-market listings continue to show MDP-REV-D in active demand, including both new and used stock.
It is a digital Speed Switch Unit / Revolution Detector / RPM Relay used in Daihatsu marine diesel-engine control and protection systems.
The genuine packaged unit is marked DC24V, and Meiyo’s official MDP-REV specification uses 24VDC ±25%.
They are the three programmable revolution-detection points provided by the speed switch. Their exact functions depend on the engine control configuration.
The Daihatsu manual identifies #14L as a start-up interlock contact.
Yes. The unit supports a 4–20mA analogue output.
It can be used as part of diesel-engine overspeed protection and is frequently referred to in marine engineering as a speed relay / overspeed relay / speed measuring unit.
Yes. The instruction manual includes pulse-sensor connection, and marine installations use pickup sensors to detect engine rotational speed.
The official MDP-REV specification uses a 4-digit red LED display.
The MDP-REV family supports programmable RPM settings up to approximately 9990 min⁻¹ depending on configuration.
Yes. A documented 8DK-20E auxiliary-engine parts record lists MDP-REV D, 24VDC, 3.2W.
A DC-32 engine operation-manual package contains the MDP-REV-D Speed Switch Unit manual.
It is a reference printed on the genuine Daihatsu packaging for this Speed Switch Unit-D DC24V assembly.
It is another reference printed on the genuine Daihatsu package and is useful for exact spare-part searching and RFQs.
Not always. Pulse number, ratio, speed thresholds, hysteresis and output settings must be checked and programmed for the specific engine.
SM MARINE SERVICE™ supports worldwide supply and sourcing of Daihatsu MDP-REV-D Speed Switch Units and related marine diesel-engine control spare parts, subject to stock availability.
Daihatsu MDP-REV-D Speed Switch Unit is a digital marine diesel-engine RPM detector / speed relay / revolution detector used for engine-speed monitoring, overspeed protection and startup/interlock logic. The genuine Daihatsu assembly shown here is marked DC24V, 00853-001, 7835149 and FD-02-406. The MDP-REV family provides a 4-digit digital RPM display, three programmable speed-detection points, #14L startup interlock, 4–20mA analogue output and revolution-frequency output. SM MARINE SERVICE™ supplies genuine, used, refurbished and reconditioned Daihatsu speed switches and marine engine automation spare parts worldwide.
SM MARINE SERVICE™
Marine Automation & Navigation Equipment Supplier
Available Condition:
• New Equipment • Used Equipment • Refurbished Equipment • Reconditioned Equipment
Stock Location:
• Bangladesh • China
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Contact Information
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