Pulse width modulation to analogue converter board

Most small micro-controllers do not have actual D/A converters to produce analog outputs. Instead, they provide PWM signals that can be converted to analog values using an LP filter. This approach is good enough to generate 0-3.3V or 0-5V analog outputs (depending on the logic level of the controller) to control small powered devices. Still, it is unsuitable for interfacing with high power systems, such as VFDs or Servo controllers for electric motors. These systems typically have 0-10V analog inputs and expect galvanic isolation between the drive and the controller for improved performance and safety.

These boards provide adequate isolation and level conversion to control the speed of up to three separate motors (or other actuators) safely and precisely. The board requires a 24Vdc power supply and delivers an output level adjustable between 5V and 12V at full scale, making it directly compatible with most commercial drives. Each channel is totally independent and optically isolated from the other and the controller. When the VFD provides its own “wetting” voltage (typically 10V), the converter can be powered directly from this supply bypassing the internal regulator. The maximum output voltage is the same as the power supply in this setting, and no level adjustment is necessary.

The board uses standard 0.2″ screw terminal boards. It can be housed in a commercial DIN rail mounting plastic enclosure for easy integration into electrical control cabinets. (See options when ordering)

FEATURES

• Adjustable output level
• Optical isolation
• Independent channels
• Through hole components
• Socket mounted ICs
• Sturdy construction
• Fits in standard DIN rail enclosure (see options)

SPECIFICATIONS

• Number of channels :1, 2 or 3
• PWM input: TTL level. Max frequency 1KHz, 5mA @ 5V, 1Kohm Impedance
• Output: Adjustable 0 to 5..12V. 1 kOhm impedance.
• Linearity: 2% FSD
• Isolation: Min. 500 Vac
• Power: Nominal 24 Vdc (Acceptable range 17 to 30Vdc)

DIMENSIONS (board only)

• 1 channel - 3.400 x 1.300 in. (87 x 33 mm) 0.52 oz (0.015 Kg)
• 2 channel - 3.400 x 1.950 in. (87 x 50 mm) 0.90 oz (0.025 Kg)
• 3 channel - 3.400 x 2.700 in. (87 x 69 mm) 1.90 oz (0.055 Kg)

USAGE

Each channel is totally independent, therefore they can be connected to different controllers (if required). The same applies for the outputs.

ENCLOSURES

The boards can be delivered bare or mounted in a DIN rail plastic enclosure. Select your option when ordering.

Alternatively enclosures can be purchased through distributors or online:

• Bud Industries - #DMB4770, #DMB4771, #DMB4772
• Digikey: DMB4770 - #377-1807-ND, #377-1808-ND, #377-1809-ND
• Mouser DMB4771 - #563-DMB-4770, #563-DMB-4771, #563-DMB-4772
• Newark DMB-4771 - #12T6235, #12T6238, #12T6241
• Velleman: GD2MG, GD3MG, GD4MG
• CamdenBox: CNMB/2/kit, CNMB/3/kit, CNMB/4/kit

OPTIONS

The boards are available in 1, 2 or 3 channel versions. All channels are functionally equivalent.