LCD Meter

David built this LCD meter from the ground up using a 40 pin controller IC driving a LCD panel. It works quite well as a DC voltmeter.

BANG!

Too much Ozzie....we were running fine at full volume until we decided to measure the supply current and managed to short something out....BANG!....spares are becoming a more important purchase consideration...

Power Supply for Audio Amp

David built this new supply over the weekend to power an audio amp based on the STM TDA7293 IC. With a peak output of 100 watts it's amazing what $5.78 can buy....I bet there is some profit margin left in consumer audio products...The supply provides +/- 30vdc for the amp plus other outputs.

Tri-Color Surface Mount LED

Located in the center of the green adapter board is a tiny surface mount LED; a red, green and blue device. David successfully soldered this by hand. No doubt his eyes are better than mine and his hand much steadier!

Toroidal Transformer Power Supply

A new power supply David built with regulated 12 vdc and 5 vdc outputs.

Tuned-Port Subwoofer

Our first effort building a tuned-port subwoofer by combining scavenged speakers and housing with a port tuned to 80 Hz. The speaker wires are seen coming out of the port (temporarily).

Fall Visitor

One of three visitors and likely winter guests at our garden pond.

Another departure

A new design by David: the tower of large LED's will be controlled by an IC that responds proportionally to a voltage input. An Op Amp front end will match inputs, for example an iPod. The short tower on the left has volume (top), tone and power controls for a solid-state amp to be built.

Air Cannon

There is not much of a connection ROV's but a fine example of a compressed-air ping pong ball cannon. It delivers very good range when charged between 40 and 60 psi. Of course the obvious question is, can we build a bigger one?

Another Application Idea

David engineered this circuit consisting of an ADI accelerometer (top) feeding an opamp with gain set to match the 2/3 Vcc operating point of the 555 timer modulation input. The 555 pwm output drives a 15 amp darlington power transistor (right) with a 12vdc incandescent lamp for a load. The circuit is perfectly balanced. Our plan is to secure the accelerometer underneath our trampoline with light weight shock cord. The result is lighting that responds to the users bouncing and jumping.

Better Soldering Work

David sent this to me via his phone to show how much better he did (2) at soldering an accelerometer on to an adapter board than I did (1).

Power

You can never have too much power......

Electron Beam Deflection

As part of our investigation of electron tubes, we have a small CRT (bottom center) to experiment with. We have 5KV (right meter) for the second anode supplied from a cable tester (large black box). The two white dots on the screen are a result of driving a single deflection coil with a 555/power transistor circuit. Note the small stream of smoke in the lower right corner as we exceed the power capacity of a current limiting resistor.

Revised Pressure Chamber Design

Here's the revised design for the pressure chamber with a cable bulkhead. Cables will first enter the the cable bulkhead via a water proof seal. Connections to the pressure chamber will be via sealed connectors.

Proposed Dome Mount Design

This shows the current design to mate the acrylic dome to the body of the pressure chamber. A double seal would be formed with a gaskets (not shown) under the ring and under the flange of the dome.

Time Delay Water Switch

This is an earlier design David created. It is a normally-off switch. The delay is activated as the switch is submerged. Inside the chamber is a large spring compressing two copper contacts seperated by an Alka-Seltzer tablet. One possible application is to turn on the underwater camera lights after the craft has decended below the surface.

Underwater Video camera & Lamp

This was our first design for an underwater video camera and light source. These were used during our first test dive down the well.

First Dive Video

This is a video from our first test dive with our first underwater video camera design. This dive is in a residential fresh water well approximately 30 feet deep.

Pressure Chamber Model

This is the first draft of a design for a new pressure chamber rendered in SketchUp. We have an estimate from a local welding shop to fabricate the main body out of aluminum or stainless steel. The bottom section will be a double bulkhead chamber for connections to the surface cable and to sensors/actuators on the ROV.

Unipolar Stepper Motor & Control Circuit

David constructed this circuit today using a uni-polar stepper motor IC (seen upper right) he selected and ordered earlier. This device, an Allegro/Sanken SLA7026M, is a high power (3.0 amp peak) controller. It does require a bit more support circuitry as it does not have a translator on board and the (step) truth table requires control of four inputs simultaneously to sequence each step. Initially, it appeared that the circuit was operating as the holding torque on the motor could not be overcome manually. We may have suffered a chip burn-out for unknown reasons as there is no further response; investigating now. The very large stepper motor seen in the upper left is out of an HP Laserjet 3si (a monster).

Underwater Structures to Investigate

There are lots of interesting structures underwater that suggest investigation. This is an example in the channel fairly deep into the harbor. There are some remarkably large features in the sound that are also high on our target list.

Digital Potentiometer Prototype

David researched and found a digital potentiometer by Intersil (X9511WP)-it arrived today. It’s a 10K ohm device with 32 up/down steps controlled by the three button array David salvaged from a printer (seen on the left). It works flawlessly with about 330 ohms per step. This device is limited to a wiper current of only 1ma. I also connected it to a 555 timer in an astable configuration. By replacing the two timing resistors with the digital pot, we can vary the ratio of the two resistors. The duty cycle is determined by this ratio giving good motor speed control via a mosfet. It works great and we think it is a better solution for control of the dive motor speed over a continuous mechanical potentiometer.

SOIC Carrier & Test Board

This is a closer view of the SOIC IC packaging, clamping test adapter (black) and prototype board.

Stepper Motor Control Circuit Prototype

We ordered a 3M prototype socket for the Allegro stepper motor controller 24 pin SOIC package and constructed a test board with wires for each pin. This assembly is seen in the lower left of the image. Parameters are set as: slow-decay mode (PFD high); full-step (MS1 &MS2 low); Rt=56K & Ct=680pf; Vref=4v; Rs=1.25ohm.

Validating the design, I measured V sense resistor=.32V and I motor supply=300ma which matches the design figures closely. Also, the square wave on both sides of the motor indicates the pwm is working. I tied the STEP input high with a pull up resistor. I have a 555 timer running at a very low frequency sucessfully driving the STEP input resulting in discrete rotation. Our objective is to use a stepper motor to control a claw on the ROV for grasping objects underwater. We are gathering a fine collection of stepper motors from old printers cast off at the local recycling station.

Note the black power supply (0-17vdc) at top that David built recently for our lab projects.

Mini ROV Design

David recently created this design for a mini-ROV. The concept is for a small ROV with a four to five inch diameter pressure vessel (sketch not to scale) that can be launched from a larger ROV. The diagram shows a complete mini-ROV using a single motor for propulsion and a parallel up/down-right/left rudder system with linkage controlled by stepper motors. The mini-ROV has a video camera in the front dome with lighting and blue LED’s. In the middle, circuitry can be seen for the stepper motor controller, motor speed controller, video-to-fiber converter and at the top a fiber controller with a cable back to the main ROV (including power).

David's ROV Design First Sea Trial

This is a second ROV design David created and assembled. This image shows the first sea trial this weekend held off Misery Island. Two propulsion motors and the chum cannon are seen mounted on the frame.

Today we launched the original ROV design for the first time in Manchester Harbor. To reduce buoyancy, we drilled holes in the lower frame to let water in. We encountered a small water leak in two of the bulkhead cable seals. The lesson learned is that we must use a full length connector seal (including a silicone filled tube beyond the barb) and cannot get away with a short version!

We face a critical path challenge as we do not have a working match of ROV buoyancy to decent motor power. We will experiment with weights and likely a decent second motor.

Capacitance Decade Box

David built this capacitance array for lab experiments today.

Fiber Optic Link

We've started work on a fiber optic link. The scope trace shows the response of our PIN silicon photodiode receiver circuit (top) to the IR diode transmitter (bottom). This result is with the detector and transmitter in very close proximity. The next step is operation with a fiber cable (we have a 10m patch cable to experiment with).

Variable Power Supply

This weekend, as an additional project, David built the variable power supply shown in the photo. It delivers a continuously variable voltage from 1v to 17v by adjusting the silver potentiometer shaft.

Dive Throttle Arm

This is the throttle arm young David designed and constructed. Note the fine thread on the brass rod that supports the black handle. This was his first time using a tap & die set and he did a exceptional job threading the shafts and tapping the aluminum arm.

PWM Motor Control Board

This is a photo of the control circuit board for the ROV dive motor. The dive motor is located in the center near the bottom of the ROV. It is a conventional pulse width modulation control circuit. The mosfet has substantial copper heat-sink surface area attached. This is required due to the high current drawn by the motors when driving a propeller underwater (average 2.5 amps). The rate at which the ROV descends is controlled by a potentiometer located on the surface control panel. In addition, we have successfully prototyped real-time modulation of the pulse width (hence motor speed) by an Analog Devices accelerometer (with op amp stage to amplify and transition between different circuit supply voltages). This design shows very good sensitivity to acceleration in the vertical axis. It will be incorporated to provide increased stability of the platform for the video cameras and FST or future manipulators.

Depth Pressure Vessel

This is the completed depth pressure vessel. The fitting on the top will connect by tube to a pressure sensor (Honeywell) which has a linear voltage output of 15 mv/psi. At 33 feet, the volume of air will be half the total. We need to build an op amp circuit to drive the signal to the surface to a digital panel meter on the control console.

Video Camera Case

This is the newest underwater case design for our video cameras. I tested this today in 12 inches of water for 30 minutes (in the basement work sink) with no signs leaking. I used 2 inch acrylic tube with matching rubber washers found at the local hardware store. The next step is to build an internal support for the video camera and decide on the best option to seal the external wire feed.

FST

This view shows a nearly complete FST assembly with the plunger release mechanism (aluminum arm) and trigger solenoid (white cylinder on top). We made good progress today fabricating a housing for the trigger solenoid and initial mounting on the FST body.

Side View of ROV

This is a side view of the ROV. The starboard drive motor, blue instrumentation box and FST are seen in this image. Missing from this stage of assembly are the Chum Cannon, compressed air tank, depth pressure vessel, video cameras, and circuitry for motor control (with accelerometer stablilization), pressure sensors, temperature sensor, and more.

Relay Bank

This is a view of the relay bank that controls the forward/reverse drive motors. This assembly sits inside a blue plastic box located inside a waterproof case mounted on the ROV. There are two relays per motor for reverse and forward control. A large 10,000uf capacitor is (seen on the right) included to provide local instantaneous surge current vs drawing on the battery at the end of a long tether cable for every motor action.

Chum Cannon Piston

This is a view of the o-ring assembly, piston lock nut and the plate attached to the end of the piston. The quarter inch holes that let water in as the piston pushes to the right are seen as well. The brass barb fitting is the piston air exhaust.

We're using a Humphrey solenoid pneumatic valve (model 310) to control the air piston.

Chum Cannon

In our first submersion test this evening, the chum cannon worked as expected. The piston moves more slowly than in air due to the limitation of only 4 quarter inch holes for water to flow through. We did experience a small leak in the chamber. The source appears to be a failure in the acrylic end seal. The use of PVC cement is not ideal for acrylic and has repeatedly shown poor strength. Now I have to figure out how to get the water out and re-seal the end.