Matrix user forums

Hi,
I am building a timer which I have discussed on the forum, however I want to incorporate an ICSP socket in the circuit, I have
found a diagram from microchip but the values of the resistors, capacitor and diode type are missing, could anybody help me out please I am attaching the pic...


thanks in advance
Acestu

If I was you I would use 10K resistors for all ie VPP, VDD and isolation resistors.

Capacitor could be 100nF multilayer ceramic type for example.

You can only use pots or switches that are n/c on RB6 or RB7 only if via 10K resistors (Labeled as isolation circuits). The middle wiper or switch must be connected to the 'Application Circuit' side, and not directly on RB6 or Rb7

Hi Stuart

There is a similar circuit on page 27 of chapter3 in the pickit2 user guide.
You can get that from the microchip website.
Sorry dont have a exact lnk ut the manual reference is DS51553E

Hi Martin,
I am not using isolators because the pgd and pgc pins are not used on this circuit, just need to know what sort of diode to use, also just hit another problem as the
VDD pin (2) of the ICSP connector goes straight to the VDD of the pic, but there are 2 VDD connections on the 16f877a, do i connect to both of them and then connect a resister to them and board power?. I am using ISIS to make the diagram but power and ground connections are hidden, is there a way of making them visible?...

thanks
Acestu

Hi John,

I will have a search for that .....

Thanks
Acestu

Hi,

I have searched google and I cannot find anything about using icsp with isis, the problem is that device power pins are hidden and they go straight to the power rails however what if you wanted to put a resister in line ? which is what I need to do for the ICSP Header.

thanks
Acestu

HI
Did a quick search on google, lots of stuff about hidden pins, one page suggests going into the library for the component and unhiding pins, i don't use isis but heres one link http://search.edaboard.com/proteus-hidden.html

Regards
Dazz

Thanks Dazz,

I have seen those links but they don't really explain anything, in your link for example the reply is " I don't think it is possible" thanks for having a go though, I have posted on the Edaboard forum myself to see if anybody can help....


cheers
Acestu

Hello,

You can reference the power pins by dragging on power and ground terminals from the terminals toolbar. Power rails with empty string identifiers default to the common rails VDD and VSS which are also used for the micro.

Hi Benj,

Yes this is a little confusing but I will try and explain, I can add a power icon and change its name string in properties to the same name as the hidden power pins of the device ie VCC

now this allows me to further connect anything I like to the VCC, however I want to place a resistor in between the VCC pins and the power rail so I need to be able to connect both of the devices VCC pins to the resistor and the other side of the resistor to the power rail, does this m


thanks
Acestu

Hi Fellas,

I think I have sussed it out, I changed the string of the power icon coming into the board to +5 and left the hidden pins on the device to VCC, then put a +5 power icon on one end of the resisteor and a VCC power icon on the other end of the resistor and that has separated them.

What do you think ?

cheers
Acestu

Hi,

I was just wondering if somebody could tell me please what default size track should I use if I am making a double sided board in Isis, the default is set to 10th
but it seems a little thin...

thanks
Acestu

HI
A few links below
Theres an online calc here http://circuitcalculator.com/wordpress/?p=25/
heres a link to a page detailing spacings and widths http://www.frontdoor.biz/HowToPCB/HowTo ... Space.html
A pdf on overall design http://alternatezone.com/electronics/fi ... alRevA.pdf

Regards
Dazz

Hi Dazz,

Thanks for the links good finds, and thanks for taking the time, ISIS is a bit confusing because they dont use mm for the track widths they use 10th or 20th etc,


cheers
Acestu

to convert th (Thou) to mm:
*0.0254
E.g 10th = 10*0.0254
=0.254mm

If you have mm then divide by 0.0254
e.g 0.254/0.0254 = 10thou

medelec35 wrote:to convert th (Thou) to mm:
*0.0254
E.g 10th = 10*0.0254
=0.254mm

If you have mm then divide by 0.0254
e.g 0.254/0.0254 = 10mm

Hi Martin and Acestu
I think 10Thou is .254mm ( you added an extra zero)

as 10mm = approx 393Thou

an easy way to remember is 100 Thou = 2.54mm

so mm to Thou eg 5mm *100 /2.54thou =196.850 Thou
or
Thou to mm eg 50 THou*2.54 /100= 1.25mm

Formula Below
Thou= mm x 100(constant)
2.54(constant)

mm = Thou x 2.54(constant)
100(constant)

For pcb's the Thou and Mil are interchangeable, also be aware how you reference imperial units as 10th as 10 Thou are two totally different units 10th refers to one tenth of an inch which equals 100Thou or 2.54mm(notice anything here. yup its our constant converstion factor) and 10 Thou= .254mm whereas 1 Thou is .0254mm. At first glance imperial seems confusing, but to be honest i find it easier to use than the metric system.

so in summary a mil is a Thou(ish) and remember the constants 100 and 2.54 , when using for tracks always round up for a small safety factor, so if your required size came out at say 10.139485 Thou(mil) select 11 Mil or above for track
If you need more help just holler but bear in mind its been 30-40 years since i learned this stuff and about 5 years since i last used it

Regards
Dazz

Hi Dazz

dazz wrote:I think 10Thou is .254mm ( you added an extra zero)

medelec35 wrote:to convert th (Thou) to mm:
*0.0254
E.g 10th = 10*0.0254
=0.254mm

They are both the same.
0.254mm = .254mm

I used the 0.0254 for converting mm back to Thou
ie 0.0254mm = 10thou
Although I did make an error in putting = 10mm instead of 10thou

Martin

Hi Martin
yup its that extra zero or mm , personally i really struggle with metric and find imperial much more flexible, although logically metric is easier ( tubing and lathes are still imperial in the main,seems ironic when building custom motorcycles that anything built after the 70's was built to the metric standard, but all converted from imperial)
damn im getting old
Regards
Dazz

Hi Martin, Dazz,

thanks for the info, I was rather hoping that somebody would say that ISIS and ARES can work out all the track sizes for you, I have never really used it for producing gerber files before and video tutorials seem to be scarce, anyway it was £30 for ten pcbs so I have sent off my gerber files and hopefully it will be useable...

cheers
Acestu

Hi Acestu,

I haven't used Proteus for a while but I am sure you can define track sizes in the "Netlist" and "Routing Strategies" properties.
i.e. If you have a standard size for signal, power, layers, you can pre-define track width/ vias etc., and transfer this data to Ares.
I personally use Abacom Sprint Layout 6 for simple layouts (cheap, quick and easy interface but also does Gerber outputs) and Easy PC for more complex designs.
I hope this helps!

Regards

Brian