DigiLite Lesssons to be Learnt from the Past Projects
Posted: Sun Apr 01, 2012 7:33 am
First I would like to thank those involved in DigiLite (and Poor man’s DATV) to give ATV a new direction and purpose. Having been a BATC member since the 70’s and from the 90’s had wanted to get back into active ATV construction again. But had little time or knew what direction to go as it is important to have a common specification to make sure all equipment is compatible.
Having bought the BATC components, I am currently buying the remaining DigiLite components. I planned to build the F1CJN Controller as it used the common HD44780 LCD, which I have one available and was able to down load all of the support material. Where as the G8BYI design didn’t specify the LCD in the BOM or on web page, but the interface is obviously not for the HD44780. Secondly I have always had some difficulty downloading items from the DigiLite site. On clicking the green arrow button for the latest G8BYI code (or clicking on the blue hex button), I just get a very quick flash of a new empty window, but no error message to help me identify where the issue lies (site, browser IE8, firewall, etc.). I don’t know if this is a problem for others as I have not seen any forum postings on this subject. I have waited until the latest web site updates completed to re-check in case the situation improved. But probelm still exists for me.
On looking at the F1CJN design I noticed on closer inspection of the overlay diagram, that all of the PCB diagrams appeared to have some shorted pads. Being shorted to either the ground plane or to other pads. I guess that if I am correct this might be due to the creation of the PDF file. It would be useful to know if anyone else has noted this or has attempted to build this PCB with the as published PCB board diagram?
Similarly, I had been looking at the COMTECH mods information in particular the video output amp circuit and PCB, reference RX010.709. It was clear that there was an inconsistency between the circuit, overlay and PCB track diagrams. Ignoring the typo in resistor ID for the device that is not required for a split power supply. On U3 Pin3 of circuit is a 20k resistor, on overlay this is a 680pf capacitor. On the circuit and overlay there are 3 x 75R resistors. However on the PCB track diagram there are no pads for the left most 75R, just a straight track that would short out the resistor if fitted. Also the actual 680pf capacitor (C12) is connected to L2 & L3. This connecting pad is actually shorted to the ground on the PCB track diagram. Not sure if anyone has built this circuit and corrected these apparent errors
My point I am trying to make is that whilst it is OK to publish ideas, notes, and sketches if marked as such. But for technical constructional articles it is very important to make sure the information is correct. For ATV to grow and survive articles should cater for all level of members and non-members. To get active members across the UK must be an aim so that at any location it is possible to make contacts over the air with others, otherwise it will continue as a few pockets of activity for a minority of knowledgeable members. Not all members have an electronics degree or technical background that allows them to spot and correct such errors. I can visualise seeing a lot of discarded projects due to not being able to getting them to work due to incorrect information. Although generally there are people around who would help out if asked, and we now have a successful forum and the internet.
But I see DigiLite as a good start for a bright ATV future but must not be allowed to be dogged by errors in any future projects. I know we are not in a commercial business and we are “amateurs” but a little professionalism will help everyone involved in ATV.
I remember during the 1970’s when Practical Electronics and Practical Wireless magazines were full of construction articles. As a kid the frustration of having limited success in getting projects built to work. Talking to other engineers decades later it was a common theme of non-working projects. Was it that we were young, quality of components due to lack of pocket money, construction techniques, or the design? It was clear some designs were built from items in the author’s junk box and sometimes difficult to source the same components.
If my comments offend anyone then I apologise but I felt this needed to be said and back in 2009/10 when there was a shortage of copy for CQ-TV. I did start to write an article on this subject covering lack of copy, past experience of ATV, and lessons to learn. But I came across by chance the Poor man’s DATV and then later by DigiLite and the void seemed to have been filled with a new project for anyone who wanted to join in with DATV could do so.
Having bought the BATC components, I am currently buying the remaining DigiLite components. I planned to build the F1CJN Controller as it used the common HD44780 LCD, which I have one available and was able to down load all of the support material. Where as the G8BYI design didn’t specify the LCD in the BOM or on web page, but the interface is obviously not for the HD44780. Secondly I have always had some difficulty downloading items from the DigiLite site. On clicking the green arrow button for the latest G8BYI code (or clicking on the blue hex button), I just get a very quick flash of a new empty window, but no error message to help me identify where the issue lies (site, browser IE8, firewall, etc.). I don’t know if this is a problem for others as I have not seen any forum postings on this subject. I have waited until the latest web site updates completed to re-check in case the situation improved. But probelm still exists for me.
On looking at the F1CJN design I noticed on closer inspection of the overlay diagram, that all of the PCB diagrams appeared to have some shorted pads. Being shorted to either the ground plane or to other pads. I guess that if I am correct this might be due to the creation of the PDF file. It would be useful to know if anyone else has noted this or has attempted to build this PCB with the as published PCB board diagram?
Similarly, I had been looking at the COMTECH mods information in particular the video output amp circuit and PCB, reference RX010.709. It was clear that there was an inconsistency between the circuit, overlay and PCB track diagrams. Ignoring the typo in resistor ID for the device that is not required for a split power supply. On U3 Pin3 of circuit is a 20k resistor, on overlay this is a 680pf capacitor. On the circuit and overlay there are 3 x 75R resistors. However on the PCB track diagram there are no pads for the left most 75R, just a straight track that would short out the resistor if fitted. Also the actual 680pf capacitor (C12) is connected to L2 & L3. This connecting pad is actually shorted to the ground on the PCB track diagram. Not sure if anyone has built this circuit and corrected these apparent errors
My point I am trying to make is that whilst it is OK to publish ideas, notes, and sketches if marked as such. But for technical constructional articles it is very important to make sure the information is correct. For ATV to grow and survive articles should cater for all level of members and non-members. To get active members across the UK must be an aim so that at any location it is possible to make contacts over the air with others, otherwise it will continue as a few pockets of activity for a minority of knowledgeable members. Not all members have an electronics degree or technical background that allows them to spot and correct such errors. I can visualise seeing a lot of discarded projects due to not being able to getting them to work due to incorrect information. Although generally there are people around who would help out if asked, and we now have a successful forum and the internet.
But I see DigiLite as a good start for a bright ATV future but must not be allowed to be dogged by errors in any future projects. I know we are not in a commercial business and we are “amateurs” but a little professionalism will help everyone involved in ATV.
I remember during the 1970’s when Practical Electronics and Practical Wireless magazines were full of construction articles. As a kid the frustration of having limited success in getting projects built to work. Talking to other engineers decades later it was a common theme of non-working projects. Was it that we were young, quality of components due to lack of pocket money, construction techniques, or the design? It was clear some designs were built from items in the author’s junk box and sometimes difficult to source the same components.
If my comments offend anyone then I apologise but I felt this needed to be said and back in 2009/10 when there was a shortage of copy for CQ-TV. I did start to write an article on this subject covering lack of copy, past experience of ATV, and lessons to learn. But I came across by chance the Poor man’s DATV and then later by DigiLite and the void seemed to have been filled with a new project for anyone who wanted to join in with DATV could do so.