Inplane Mask Head (A2052) Manual

Contents

Description

The Inplane Mask Head (A2052) is a Long-Wire Data Acquisition (LWDAQ) Device that drives nine IRLEDs (infra-red light-emitting diodes). The A2052A-8 has nine infra-red LEDs on the back side and three 8-mm snap-in standoffs. The A2052A-12 has 12-mm standoffs. The A2052A with no suffix has no snap-in standoffs.

The A2052A has the same connector locations, LED locations, standoff locations, and board dimensions as our earlier A2034A, and NIKHEF's RASLED card. The A2052A replaces the RASLED when you upgrade to Long-Wire DAQ. The RASLED is not a Long-Wire device. One functional difference between the two boards is that the RASLED card as a green LED that turns on when the LEDs turn on.

If you want to put the snap-in standoffs into the board yourself, view our standoff installation video.

Specification

The A2052 is complies with the LWDAQ Specification.

Device Type

The A2052 is LWDAQ Device type 1 for the purpose of device-dependent jobs.

Device Elements

The A2052 LED driver is element number 0 or 1.

Command Bit Allocation

Note that the A2052 ignores DC8, which is normally the WAKE bit for LWDAQ devices. But the A2052 has only two states: off or on. The off state is equivalent to the usual sleep state.

Operation

Connect the A2052 to a LWDAQ driver (such as the A2037) or multiplexer (such as the A2046) with a LWDAQ cable. You can use shielded or unshielded. Once you are capturing images of your LEDs, you can adjust the exposure time used by the flash_job to make them brighter or darker in the image.

Example: Suppose we want to illuminate nine LEDs in series. These nine LEDs are in an existing optical assembly. We have two wires coming out of the assembly, and the LEDs take 100 mA. The A2052A provides a two-way connector (P1) for the two wires, and will source 100 mA into them when the driver instructs it to do so. Pin one on the connector, which is uppermost in Figure 1, is the negative terminal of the LED current source, and pin two is the positive terminal.

We put a two-way socket on the two wires coming out of our instrument. We plug this into the A2052A. We connect the A2052A to a LWDAQ driver with a CAT-5 cable up to one hundred meters long. We note the device socket into which we plug the head, and determine the device address we should use with the driver to make it communicate with our device.

To flash the light emitting diodes, we tell the driver the address of the A2052A, and the type, which is one (1). We specify our desired on-time for the LEDs, and instruct the driver to execute a flash_job.

We never have to worry about the A2052A being awake or asleep. It is automatically asleep when it is not driving LEDs.

Functions

The A2052A flashes its bottom-side LEDs during a flash job. It comes with either 8-mm or 12-mm standoffs, and we can order other lengths as you require.

The A2052 is asleep whenever it is not driving its LEDs, so you never have to send it a sleep command. To measure the propagation delay of signals travelling from the driver to the A2052A and back again, you execute the loop_job and read the loop time out of the driver.

Reliability

We intended the the A2052 to pass 80 mA through its nine LEDs. We miscalculated, and it passes 110 mA instead. The extra current, combined with the low forward voltage drop of the LEDs we used in our ATLAS circuits combined to make our A2052 vulnerable to damage when left on for more than a few hours. We describe this failure in the Reliability section of our Proximity Mask Head (A2045) Manual. When an A2052 suffers severe damage through over-heating, it's optical power output drops to 1% of its undamaged value. By replacing one of the 47-Ω power resistors (R3 and R4) with a 100-Ω resistor, we can stop the over-heating. As reported here, an A2052 with the 100-Ω resistor will remain on for at least a week with no damage.

Power Consumption

We picked an A2052A at random and measured its power consumption in two states.

We intended the A2052A to pass 80 mA through its LEDs, but we miscalculated, as we describe above.

Electronics

You will find the A2052 circuit diagram here, and printed circuit board files here.

Here is the A2052 circuit diagram.

Here are the two available printed circuit board layouts.