Repair of a Channel Master D2A

After studying Amazon I picked this converter because the only negative review was over the interpretation of the description of what the unit was for.

Channel Master D2A

It has worked well for years until it started to continuously reboot.  Rather than just replacing it I decided to attempt to repair the unit. I was pleasantly surprised when I opened the unit and found a separate power supply with through hole components.

Inside

Not only was there a separate power supply board but the supplies are labeled at the connector.

Output Capacitors

I made some measurements and found the power supplies output high. I static checked the components in the output side of the power supply and decided I would take a chance and change all the caps on the output side.
C10, C11, C13-470uf @ 16v
C12=1000uf @ 10v
C7=220uf @ 25v
C8=100uf @ 25v

Once all the capacitors where changed the unit worked fine.  I wasn’t surprised that the capacitors had gone bad because of the heat generated by the power supply.

Sub Contractor of a Prime Contractor on a Federal Contract. My Sad Story.

Before I share my story, I will share my advice on being a Sub Contractor for a Prime Contractor on a Federal Contract.  Assume that you will not get paid without a FIGHT.  So make sure that you take steps to insure you get paid even if the Prime Contractor hops a plane to Cameroon with the money.  A payment bond or the government pays into an Escrow account that the payments are distribute from and that the Prime Can’t empty by himself. Bottom line, you can not rely on the Federal Government ensuring that you will get paid.

Toward the end of December 2012 we were approached by a Federal contract holder, 8a Certified,  needing help with a scanning project in Atlanta.  This was a ongoing project lasting several years.  We started in December, submitted an invoice at the end of month and at the end of January 2013 we got paid as stated in the contract.  This should have been a good sign that they where going to up hold their end of the contract.  We continued the work and the Prime brought in another scanning company to take over his employees and to work along side us.  After he did that we slowed down our plans to scale up production.  We billed him at the end of January as did the other scanning company.  We continued through February 2013 at the end of February we submitted our invoice and waited for payment for January, so that we could scale up production. Payment did not happen.  We attempted to contact the Prime contractor, no response.  We then inquired with the contracting officer for the Government and found out he got paid just after the 15th of February. At the beginning of the second week of March we sent an extremely aggressively worded email to the Prime which got a response that they would be sending payment Friday.  Needless to say that payment never arrived.  We filed a complaint with the government but it was too late to stop the payment directly to him for the February invoice.  We ceased operations on the project until our contact could be reached.  Two weeks went by with no response from him.  We got word that the other company can not reach him nor have they been paid for January or February.  So at the beginning of April we went to the site to remove our equipment and to turn in our security badges.  At that time we where informed that the Prime had not submitted an invoice for March and that they would be cancelling his contract. Unless the Prime submits an invoice we would not be getting paid for March since we don’t have a contract with the Government. 

In the Months since we still can not reach the Prime Contractor.  All letters have been sent back as “Moved no forwarding address”, phone numbers have been disconnected.  We went as far as sending a demand letter to the registered agent listed on their corporate filings for the state of Virginia.  

How it stands now, the contract has been canceled and the president of the company we where a subcontractor for is gone as well as his employees.  It goes without saying that I didn’t get paid. All it seems to remain of the Prime contractor and it’s owner is a web site and a trail of short sold residences of the owner. However, The contracting officer would like to give us a positive review but we where not the Prime contractor.  

Adding an Aux Garage Remote.

My purpose for this project is to add an additional remote controller to my garage door opener without making any permanent changes to the opener.  In this project I used the Visitect RF300R receiver and matching remote.

Decoding the outputs.  The receiver has 2 data outputs and an enable output.  The enable goes high when either button is depressed.  Data 1 and Data 2 latch high depending on which button was pressed last.  To allow me to add additional features later I decided to use the enable and Data 2 to control the relay to trigger the opener.  To keep things simple I constructed a simple AND circuit so that both signals had to be high in order for the relay to close.  This can be seen in the circuit diagram below.

Circuit Diagram

The AND circuit is made up of two transistors and the output of the AND is the relay. The relay contact is wired across the existing button on the wall for the opener.

Operation is pretty simple push the 2nd button and the relay closes for the duration the button is held.

Receiver and Remote

Circuit boards

Conclusion: This unit has proven to be more reliable than the internal remote controller. This unit also has proven to have a range over 50 feet. However post 9-11 I would not even try to go through any type of security with the remote that is paired with this receiver due it’s unusual extendable antenna on the remote.

Remote Control Door Latch

This is a hack I did to control a 12 vdc electric door strike.  Since I was doing this on the cheap parts on hand where used. I used a surplus power supply and remote control (Key Chain Remote).  The only problem using this remote control is that it’s output once turned on will stay on until it is turned off.  I rather have the output on only for a short time and then turn off.  So I added some circuitry to accomplished this.  I also had to modify the relay in the remote module so that it connects the output wire to ground instead of 12 volts.I did this by isolating the relay contact connection from the 12 volts and then ran a wire from the relay contact connection to the black wires of the remote.

This is the circuit I came up with to keep the latch coil from being left on.

I am not worried about the mosfet operating in it’s analog region since the current through the relay is very low so the Mosfet will not get warm enough to be a problem.  (The device I used was a 10 Amp Mosfet.  It’s what I had on hand.) Also it should be noted that the coil for the latch has to be connected so that the circuit will function correctly.  

Operation:  On button is pressed door strike retracts to release the door. If the Off button is not pressed the circuit times out after 12 seconds and the door release latches back and the circuit locks out until the off button is pressed. The preferred method was to press the off button on the remote so that it would reset and be ready for the next activation.  In practice this worked fine, in fact this unit was used for over a year until we relocated the office.

Conclusion: If I did it over I would use a lm555 as a on shot so that the turn off time for the mosfet would be faster. Below is what the relay K1 voltage looks like when it is allowed to time out.
For over 2 seconds the mosfet is operating in it’s linear region. If the load was large enough it would actually cause the part to heat up noticeably, but being over-sized by around 800%  it’s not a problem powering that small pc board relay.

Louder Doorbell Hack

This is a hack I did to make a wireless doorbell loud enough to be heard over loud equipment and to give a visual indication of which door button had been pressed. For the visual indication I used two 4 inch CCFL tubes and for the sound I used a compact Siren. For the doorbell I chose the GE wireless Door Bell with two wireless buttons.

This is what it looks like inside. The 14 pin IC is a 4011. By looking at the outputs of the NAND gates I found that Pin 4 Toggles with any button push and pin 10 toggles when I press the back door button. I chose to use a MicroChip PIC processor to decode the outputs to keep the parts count down and because I had them on hand. I started by attaching wires to the circuit board in the doorbell to pick up the signals from the CD4011 and provide power to doorbell from the decoder and drivers.

I built the circuit on a perf board and mounted it to a piece of angle aluminum. Every thing gets put into a circuit breaker box I stripped all the guts out of. Function: When Front door button is pressed the siren sounds for a set time leaving the white lamp on for a bit longer. When the Back door button is pressed the Siren sounds for a set time leaving the blue light on for a bit longer.

Results: The unit has performed well since it was connected. Couple changes I would like to make. 1) Install a connector on the Doorbell and the box so that the actual doorbell can be located in a different location than the box. 2) Clean up the program so that white lamp does not flash when the back door button is held down (not been a problem so far). 3) Clean up the power supply design.

Source Code:

;Door bell decoder
;Written for the PIC12C671 running in internal 4mhz mode.
;By W.H.- April 2006
list p=12C671
include p12C671.INC
;Define configuration bits.
__CONFIG _MCLRE_OFF & _CP_OFF & _PWRTE_ON & _WDT_OFF & _INTRC_OSC_NOCLKOUT
;Define variables
cblock 0×20
TIC, TEMP, SIGNAL, BEAT, OUTPUT,W_TEMP,STATUS_TEMP
endc
;Define Macros
SWB0 MACRO
BCF STATUS,RP0
ENDM
SWB1 MACRO
BSF STATUS,RP0
ENDM
PUSH MACRO
MOVWF W_TEMP
SWAPF STATUS,W
MOVWF STATUS_TEMP
ENDM
POP MACRO
SWAPF STATUS_TEMP,W
MOVWF STATUS
SWAPF W_TEMP,F
SWAPF W_TEMP,W
ENDM
;Reset vector
ORG 0×000
GOTO START
;Define interupt vector
ORG 0×004
GOTO INTER
;Define code start
ORG 0×008
START CALL CALIBRATION
SWB1
MOVWF OSCCAL
SWB0
NOP
SWB1
MOVLW B’00001100′
MOVWF TRISIO
MOVLW B’10000111′
MOVWF OPTION_REG
MOVLW B’10100000′
MOVWF INTCON
MOVLW B’00000000′
MOVWF PIE1
MOVLW B’00000111′
MOVWF ADCON1
SWB0
MOVLW D’0′
CLRF TMR0
CLRF BEAT
CLRF TEMP
CLRF TIC
LOOP BTFSS GPIO,2
MOVLW B’00010001′
BTFSS GPIO,3
MOVLW B’00010010′
MOVWF OUTPUT
MOVF OUTPUT,F
BTFSS STATUS,Z
GOTO TIMEOUT
CLRF TIC
GOTO LOOP
TIMEOUT NOP
;Check to see if time is up.
MOVLW D’38′
SUBWF TIC,W
BTFSC STATUS,C
BCF OUTPUT,4
MOVLW D’230′
SUBWF TIC,W
BTFSC STATUS,C
GOTO CLEAR
MOVF OUTPUT,W
GOTO LOOP
CLEAR CLRF OUTPUT
CLRF TIC
MOVLW D’0′
GOTO LOOP
;Interupt routine*****interupt every .0653seconds******
INTER PUSH ;Interupt routine
BCF INTCON,7 ;Turn off interupts
BTFSC BEAT,5
INCF TIC,F ;Increment time one
MOVF BEAT,W
MOVWF TEMP
BTFSS TEMP,5 ;Toggle
BSF BEAT,5
BTFSC TEMP,5
BCF BEAT,5
MOVF OUTPUT,W
IORWF BEAT,W
MOVWF GPIO
MOVLW B’10100000′ ;Turn on interupt and clear flag.
MOVWF INTCON
POP
RETFIE
CALIBRATION
END

Steve Jobs 1955-2011

Wednesday we lost an Industry leader and pioneer. I fear that he may not see a pioneer of his caliber again.  From the early days of computers he defined the industry. Even with his departure he continued to be a pioneer in what ever he did. Upon his return to apple he continued to be a pioneer and boldly lead Apple from the verge of bankruptcy to a company with the a market cap greater than Exxon. He redefined music with i-tunes and the iPod. He defined what the smart phone is with the introduction of the iPhone. And created a new market with the iPad.

If the measure of a mans worth is all the lives he has touched and his deeds, then Steve Jobs was a great man. May his legacy live on.

My condolences go out to his wife, children, sisters and employees of Apple.

For more about Steve Jobs got to CNET News http://news.cnet.com/8301-13579_3-20116336-37/apple-co-founder-chairman-steve-jobs-dies

Don’t Click that Link Don’t Even Think About It

If  you have been around on the net for a while you already know this.  But, if you haven’t run across your spam filter is working well.

We get email like this all the time.  The below email is typical of this kind of scam.  What they want you to do is to click on the attachment and download it.  However if you look closely at the icon you will notice that is shows a block in a clamp.  This is the icon for a ZIP file.  This is a compressed file.  Since it is compressed the contents of the ZIP file are not decompressed to be scanned fine and slips past the Virus protection.  This is useful if you are sending certain types of files that the virus scanners tend to block regardless of the nature of the file. (ie.  a patch or batch file)  In this case this is most likely malicious code.  So beware of attached files.

This is a post notification
Post notification No.72166
The company could not deliver your package to your address.Your package has been returned to the Post Express office.The reason of the return is “Error in the delivery address”
Attention!Attached to the letter mailing label contains the details of the package delivery.Please print out the invoice copy attached and collect the package at our office
Thank you,Post Express Service.

Also in light of other security breaches, such as Epsilon.  If you get an email from a company you do business with open another tab and go there directly and do not use the link in the email.  Spammers now have you email address and know which companies you do business with.  So just don’t be careful be paranoid.