Hello everyone, some time ago I made a prototype of the programmer with some modifications of the original, I only left space for the 40-pin pic16f18875 and some headers to be able to test it in an independent circuit where all work fine.
I left you some attachments.
Finally once everything was working I decided to make a new design with SMD components but I have problems trying to add the micro usb. The device connects and disconnects several times at random.
I tried directly connecting a usb cable with each of its cables to the D + and D- pins and this one recognizes it perfectly, apparently it has to do with some kind of interference from the microusb female connector.
In the first circuit I used a connector similar to the arduino one where the shield is not connected to ground and yet it works ok and that is why in the design of this new pcb I did not add the shield to gnd.
Could this be a problem? In the same way I did tests connecting a shield cable to ground but I do not see a difference. Could you explain the importance of it?
I was reviewing datasheets, and I found this one from a Microchip development board called Curiosity HPC.
where I can see the following circuit in the connection to the usb but I have no idea what it is for, does anyone know?(attached).
Finally I would like to clarify that without thinking it well I decided to put on the lines from D + and D- to L1 and C6 which are the inductor and the usb capacitor, obviously this should not be done since the inductor could interfere with the lines.
In the image I disconnected them but the problem seems to have to do only with the usb connector.
In this new design I decided to remove the VDDU to focus only on external circuits with external power supply, I also added a circuit that allows me to obtain a safe voltage output with a short circuit protection, limiting it to a maximum of 400mA.
I want to share this design with you however I ran into this problem on the way.
As an extra piece of information I am soldering everything with a soldering iron by hand since for now I do not have a heat gun and perhaps the flux that I am using can leave residues between the usb pins, however, I clean them with 99% alcohol and a brush. I checked continuity with a trimmed male usb and everything is in order, apart from there are no short circuits. Any extra help and comments on what they think of the design are welcome.
I leave here some of the SMD componentes I used to give me an opinion.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Anonymous
Anonymous
-
2020-12-31
I finally found the problem, be careful with the flux especially if it is a cheap one. A part of flux accumulated on the bottom of the connector and created these undetectable problems. I leave you a video of the device. Finally for reasons of practicality I left L1 and C6 where they were and there seem to be no problems, in a new version I will fix that.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Regarding the maximum voltage limitation I would try to change the inductor: it is intended for high frequency filtering, with a maximum current of only 25mA.
At 12V it will certainly saturate.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hi, in last 5 years I maid my self or with my frend more than 10 OP from 0.9.0 to 0.11.0 version, but I never had problem with them. Some time ago I write on this forum I made a mistake on a board with ICSP and burn the 18F2550 on open programer BUT WAS MY FOULT. To not happend again I change the output rezistor of 100R with 220R , and now if there is an external mistake 5V /220R = 22ma <25ma witch can drive the 18F2550.
Also I use 180uH inductor but the condenser MUST BE LOW IMPEDANCE to not permit some autooscilation. 47 or 100uH minim 25V and LOW ESR
Thanks again to Alberto for his great job , it is a wonderfool programmer
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hi, in last 5 years I maid my self or with my frend more than 10 OP from 0.9.0 to 0.11.0 version, but I never had problem with them. Some time ago I write on this forum I made a mistake on a board with ICSP and burn the 18F2550 on open programer BUT WAS MY FOULT. To not happend again I change the output rezistor of 100R with 220R , and now if there is an external mistake 5V /220R = 22ma <25ma witch can drive the 18F2550.
Also I use 180uH inductor but the condenser MUST BE LOW IMPEDANCE to not permit some autooscilation. 47 or 100uH minim 25V and LOW ESR
Thanks again to Alberto for his great job , it is a wonderfool programmer
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hello everyone, some time ago I made a prototype of the programmer with some modifications of the original, I only left space for the 40-pin pic16f18875 and some headers to be able to test it in an independent circuit where all work fine.
I left you some attachments.
Finally once everything was working I decided to make a new design with SMD components but I have problems trying to add the micro usb. The device connects and disconnects several times at random.
I tried directly connecting a usb cable with each of its cables to the D + and D- pins and this one recognizes it perfectly, apparently it has to do with some kind of interference from the microusb female connector.
In the first circuit I used a connector similar to the arduino one where the shield is not connected to ground and yet it works ok and that is why in the design of this new pcb I did not add the shield to gnd.
Could this be a problem? In the same way I did tests connecting a shield cable to ground but I do not see a difference. Could you explain the importance of it?
I was reviewing datasheets, and I found this one from a Microchip development board called Curiosity HPC.
where I can see the following circuit in the connection to the usb but I have no idea what it is for, does anyone know?(attached).
Finally I would like to clarify that without thinking it well I decided to put on the lines from D + and D- to L1 and C6 which are the inductor and the usb capacitor, obviously this should not be done since the inductor could interfere with the lines.
In the image I disconnected them but the problem seems to have to do only with the usb connector.
In this new design I decided to remove the VDDU to focus only on external circuits with external power supply, I also added a circuit that allows me to obtain a safe voltage output with a short circuit protection, limiting it to a maximum of 400mA.
I want to share this design with you however I ran into this problem on the way.
As an extra piece of information I am soldering everything with a soldering iron by hand since for now I do not have a heat gun and perhaps the flux that I am using can leave residues between the usb pins, however, I clean them with 99% alcohol and a brush. I checked continuity with a trimmed male usb and everything is in order, apart from there are no short circuits. Any extra help and comments on what they think of the design are welcome.
I leave here some of the SMD componentes I used to give me an opinion.
BC547-> SMD BC847
BC557-> SMD BC857
diode-> 1n5817 SMD
inductor -> SMD
https://lcsc.com/product-detail/Inductors-SMD_FH-Guangdong-Fenghua-Advanced-Tech-CMI321611J101KT_C128802.html
I hope you can help me.
Last edit: Sebas Alvarez 2020-12-31
I finally found the problem, be careful with the flux especially if it is a cheap one. A part of flux accumulated on the bottom of the connector and created these undetectable problems. I leave you a video of the device. Finally for reasons of practicality I left L1 and C6 where they were and there seem to be no problems, in a new version I will fix that.
https://estliveupsedu-my.sharepoint.com/✌/g/personal/malvarezf_est_ups_edu_ec/EVYidf_wkHdNt0SflRUfiU4BzSSWvmd0i80IkdShIHHRig?e=XAm0ee
Regarding the maximum voltage limitation I would try to change the inductor: it is intended for high frequency filtering, with a maximum current of only 25mA.
At 12V it will certainly saturate.
Hi, in last 5 years I maid my self or with my frend more than 10 OP from 0.9.0 to 0.11.0 version, but I never had problem with them. Some time ago I write on this forum I made a mistake on a board with ICSP and burn the 18F2550 on open programer BUT WAS MY FOULT. To not happend again I change the output rezistor of 100R with 220R , and now if there is an external mistake 5V /220R = 22ma <25ma witch can drive the 18F2550.
Also I use 180uH inductor but the condenser MUST BE LOW IMPEDANCE to not permit some autooscilation. 47 or 100uH minim 25V and LOW ESR
Thanks again to Alberto for his great job , it is a wonderfool programmer
Hi, in last 5 years I maid my self or with my frend more than 10 OP from 0.9.0 to 0.11.0 version, but I never had problem with them. Some time ago I write on this forum I made a mistake on a board with ICSP and burn the 18F2550 on open programer BUT WAS MY FOULT. To not happend again I change the output rezistor of 100R with 220R , and now if there is an external mistake 5V /220R = 22ma <25ma witch can drive the 18F2550.
Also I use 180uH inductor but the condenser MUST BE LOW IMPEDANCE to not permit some autooscilation. 47 or 100uH minim 25V and LOW ESR
Thanks again to Alberto for his great job , it is a wonderfool programmer