Prototype line following robot

Here is a prototype line following robot we are working on for our new engineering curriculum. It uses an arduino but the final production will be a straight AtMEGA328 on a custom board to keep cost down, programming done via SPI. Just a xtal couple of caps and a v-reg a stripped version of the arduino. I am using the QRD1114 Reflective Object Sensor, initial test indicated work best about .05" above floor sensing electrical tape against a white background, speed is about 10 feet in 3.2 seconds at 9 volts. Got one channel and one PWM working to test viability, works great got it running full steam when over a black surface and stopping when hitting a white surface. Next step I will get three channels working with two PWM to steer.

Problems ran into so far:
Used wrong FETs to drive motor, was using N-CH should have been P-CH DOE! Changed wiring to break ground instead of plus rail, used IRFZ44. stupid oversight should have caught that.

New 20x4 LCD

Just got in some new 20x4 LCD's. Nope these are not direct from china, unfortunately I can't find any good deals unless they are 16x2....very strange they use the same driver IC's I would think you could get the 20x4 about the same price maybe a couple of buck more. They are NHD-0420H1Z-FL-GBW-33V3 street price $15.50, about 10 bucks too much if you ask me.

New Toy LPKF S63

Awesome new piece of capitol equipment, so much better than the T-Tech 5000 we have. Not the the T-Tech is a bad machine (I still love the T-Tech too) it just all manual set-ups, the LPKF is totally automatic just  hit mill and it changes all bit and depth automatically. Plus the S63 has a camera on-board for inspection and feedback loop that will track fiducial, so easy multilayer boards. Also this has the dispenser unit that can apply solder paste. Total control over the Z axis we can even mill 3D objects in aluminium.

Pretty intuitive got my first board done in about 1 hour (8 min to mill board) Once I figured out the software it's pretty easy. So far I've only done single sided board but soon to have two sided done next week. I did have a problem with the camera but a upgrade on software fixed it.

The all-rounder in the LPKF ProtoMat S series is great for virtually any job in in-house prototyping. The ProtoMat S63 masters 2.5-dimensional mS63 Setupaterial machining and features a faster spindle speed of 60.000 rpm

PCB with rubout

S63 Setup

 

 

 Our S63

 I5 Lenovo running Win 8

 

 First Board

First Board

PARTS AND MORE PARTS

Just got a donation of nice part bins, been logging all parts in http://ecdb.net/login.php . Pain in the neck but it's got to be done, already I am able to find parts easier. 720 bins down and logged only 1000 left!

We won another grant!!

From: Dodd, Tim (ANF)
Sent: Wednesday, May 22, 2013 5:25 PM
To: Dodd, Tim (ANF)
Subject: Important Information- Vocational School Equipment Grant Announcement

Congratulations on being slated to receive grant funding through the Vocational Equipment Grant program! This email provides logistical information about the event this coming Wednesday as well next steps in the contract process.

*Please remember that this information is embargoed and please do not share it outside of school administrators and program teachers.*

Vocational Equipment Grant Program

Announcement Event

Massachusetts State House

Room 157

Wednesday, May 29, 2013

1:30PM

Event Location:

The event will take place in room 157 of the Massachusetts State House.  Enter through the “Hooker Entrance” at the front of the State House on Beacon St.  After going through security, turn left.  At the first bank of elevators, take a right and go down a very short flight of stairs.  Room 157 will be on the right.  Please give yourself a few extra minutes to go through security, especially as it is school group season here at the State House.

Transportation

If you are taking public transportation, the State House is easily accessible by the Red or Green lines through the Park Street Station or the Orange line through the Downtown Crossing Station.  The State House is a five minute walk up the hill.

If you are driving into the city, there are several parking garages located within a few blocks of the State House.  A database of parking garages, locations, and rates is available at: http://boston.bestparking.com.

RSVP

If possible, please email me to RSVP for this event with an estimated number of individuals who will be attending by Friday at 5:00PM.  Please let me know if your school will not be represented at the event so that I can contact you by email or phone to discuss the contract process.

Contract Process Meeting

After the event, I will hold a short meeting for recipients to discuss the contract process.

Please do not hesitate to contact me should you have any additional questions.  I hope to see you on Thursday, and I look forward to working with you!

Best,

Tim

Tim Dodd

Local Government Program Manager

Executive Office for Administration and Finance

State House Room 373

Boston, MA 02133

(617)-727-2040 ext. 35405

Tim.Dodd@massmail.state.ma.us

Follow us on Twitter:   @MassANF

For information on the Community Innovation Challenge grant program, please visit the program website:

http://mass.gov/anf/budget-taxes-and-procurement/working-for-you/community-innovation-challenge-grant

To join the Community Innovation Challenge grant interest list, send an email to:

join-fad-cicgrants@listserv.state.ma.us

Precision LUX Detector

Here is a design I made for a friend who wanted an white LED to turn on when it was dusk, but also wanted so adjustment via a pot. So off to pick a photocell, I picked a VT9ØN3 that was used in many low light applications.

Found this great app note at http://www.ladyada.net/media/sensors/APP_PhotocellIntroduction.pdf

turns out there are as couple of types of photocells the Ø material and the 3 material

Type Ø Material

This is a general purpose material. Its characteristics include a good temperature coefficient and fast response time, especially at very low light levels. Cells of this type have relatively low dark history. Type Ø material is often used in lighting controls such as nightlights, and security lighting

Type 3 Material

This is a high speed material with a spectral response closely approximating the human eye. This material is well suited for switching from one light level to another and offers our best temperature stability and response time. This material is often used in cameras and industrial controls.

Once ordered we tested the photocell characteristic curve and found the following:

Now the circuit we chose was a op-amp comparator type, this was a great circuit because we used a JFET input opamp the TL072 and current consumption was less than 1ma (our target current) and have a very crisp trigger level unlike using a single transistor or FET. We used a 25 turn precision pot to get the accuracy down to +/- 1 LUX at the set-point. In-fact a voltage of 1.625 at pin 3 (reference) was ideal for dusk at 7pm local, the photocell read about 130k ohms indoors at dusk shades open with 5.25 sqft total window area facing east+west (2.625 sqft ea) approximately 3 to 4 LUX

The protocircuit below:

Video of the circuit working:

And finally PCB

PCB FILES ZIP

BOM

 

FM Bug

Today in shop we build a simple FM bug that transmitted on the lower band of FM around 88 Mhz. Picture below is the circuit in dead bug construction, ideal for RF experiments. This did work on the breadboard but it was very unstable. The resonant (fundamental) frequency of this circuit is  around 9.777 Mhz, so how does it work on 88 MHZ? Well in RF oscillators there is something call harmonics or overtones. When a circuit is oscillating it also produces a odd multiple of that original frequency, at the same time that multiple of the frequency drops in amplitude by about half (-3db) each time it's divided in a logarithmic form.

Here is a chart to explain

MHZ Amplitude P-P Fundamental Frequency 9.78 3 Odd Multiple Times 3 29.34 1.5 Odd Multiple Times 5 48.9 0.75 Odd Multiple Times 7 68.46 0.375 Odd Multiple Times 9 88.02 0.1875 Odd Multiple Times 11 107.58 0.09375
As you can see the 9th harmonic is around 88 Mhz, as a rule of thum anything over the 11th harmonic is so small it is unusable and drifts exponentially to the fundamental and is very difficult to use unless you have a very stable fundamental frequency (ie. rubidium standard). This is also very difficult to measure with a scope, the scope will load down the circuit and change capacitance of the tank circuit. We used a frequency counter not connected to but near by the antenna and a analog FM radio receiver. Overall this was a great experiment to demonstrate FM modulation, RF prototyping and using a frequency counter.