looking for a PIC

[dhouston]

I need to replace a Sonix SN8P2501BSG SOP14 µController with a PIC, preferably one that I can use the ds30 loader with.

If I can find a PIC with Vdd on Pin 4 and Vss on Pin 11, I can probably handle the rest.

Microchip used to have a page listing all PICs with pin counts, etc. but they seem to have remodeled and it is now impossible to find anything that you do not already have a model number for.

A volunteer organization gives emergency phone dial units with pendants to those who need them. They frequently get units back without the pendant. There's a Linear garage door keyfob with the right RF frequency and, if I can find a suitable PIC, I can write a program to send the needed RF codes and they'll have a way to replace the pendants (pendant no longer made).

[spcw1234]

This might help, but those power pins are going to be tough to match.

http://www.microchip.com/stellent/id...cName=en544123

[dhouston]

Shawn, thanks for the link.

I guess Microchip thinks that's an improvement - I sure don't. It is better than nothing but not by much.

Oh well, even if I found a chip, Digikey has discontinued their print catalog, making it just short of impossible to buy anything from them.

[Jumper]

Hi,

Get any PIC in a really small package and surface mount that one on a break-out board that you later surface mount on the current footprint on your pcb. Or if you have a thru hole foot print just make a board with pins that you can solder in that place or use a IC-holder.

Then you can use any pic you like and still get the pins to be in the correct place

[dhouston]

@Jumper - the SOP14 SMD chip is surrounded by other components and there is minimal headroom so a breakout board wouldn't work even if I designed one with the correct pin mapping. Plus, the (elderly) people who will have to do the work are total novices who could probably handle direct replacement of an SOP14 size chip (with a hot air rework station) but not much else as far as SMD.

But, it turns out the Sonix chip in the keyfob is powered by 12V directly to the chip so I will have to find another way to do this.

[Jumper]

No problem.. I was more thinking of that you make the board and mount the LLC package of the pic... and then put a drop of epoxy on the top to protect it.. The board will be similar in size (just a litte bit more narrow than the normal SOP-14 leg witdh)

Then the board has plated pads on the side that allows it to be soldered on the side using a regular soldering iron.

I have a similar component today and I can upload a picture tomorrow to show what it looks like

[dhouston]

Then the board has plated pads on the side that allows it to be soldered on the side using a regular soldering iron.

How do you manage that type of pad? I've seen them but my layout software has no obvious method to create them. Also, I'm not sure they can get an iron on the existing pads.

[dhouston]

I just realized that I can ditch the DIP switch and use that space to do about anything I might need.

[ScaleRobotics]

I don't know much about them, but Microchip has the HV series, like the PIC16HV610 and PIC16HV616 for "high voltage" applications. These can run to 15 volts. They come in a 14 pin, but you would have to do something like Jumper mentions to get the pins in the right places.

[Jumper]

The hard-core way I use is I place normal hole pads for a double sided PCB in suitable positions and then make the board size so the milling machine cuts tru the middle of the pads leaving a half circle plated pad with a half hole that is also plated to be used for soldering.

I think there are other ways too but this one seems to work quite ok. If you choose a really tiny pic package then it could be possible.

[Demon]

If this goes in a keyfob, how about just making an entire new PCB?

It would mean a bit more work on your part, but be simple plug and play for the users.

And where does 12V comes from in a keyfob? That's a lot of batteries, but you have a holder for only a small one?

Robert

[Demon]

...Oh well, even if I found a chip, Digikey has discontinued their print catalog, making it just short of impossible to buy anything from them.

Why? Your ISP blocks their site? Their search feature works pretty good, haven't had a problem yet.

Robert

[ScaleRobotics]

Here's a picture of a circuit board with what Jumper is suggesting:

[dhouston]

I've seen/have a few such PCBs and assumed I could use half a normal pad - just never needed to try it - sorta fits as I'm only about half-normal, myself.

A new PCB would require a few $K for FCC approvals and I doubt these volunteers want to spring for that.

I've also suggested they look at alternatives which I've listed below in case anyone has an interest.
http://want2care.com/guardian_alert_911.html
http://cordlessworkz.com/telemergenc...rt-device.aspx
http://www.directsalesinc.com/noname2.html
http://www.elderstore.com/wireless-e...ne-dialer.aspx
http://www.amazon.com/Help-Hand-Emer.../dp/B00012K246

[BH_epuk]

As a very different suggestion have you looked at the Si4010 by siliconlabs ?

Just starting on a project using this, SiLabs do supply Gerber files for a keyfob, not sure what the usage limits are on this though

[dhouston]

As a very different suggestion have you looked at the Si4010 by siliconlabs ?

It would also need FCC approval which is far too costly.

[Demon]

I'm curious, using a different micro would not require FCC approval?

Robert

[languer]

We've tried the following with some "limited" success before as arguments for FCC: "Simple component change for obsolescence retains equivalent functionality does not require re-testing". It seems you're trying a similar approach; however, the FCC will ultimately decide what is acceptable or not (which will be expensive regardless). So if you're making the "call" whether or not to inform the FCC about the change; then the following two are equivalent (we've used them with equal degree of "success"):
-> Replacing a component with and equivalent component as long as the clocks used and/or generated by the two do not change.
-> Replacing a component with an equivalent daughter card (component built-in into a small PCB to provide proper pinout and voltage conversion) as long as the clocks used and/or generated by the two do not change.

And yes I do agree with Robert, using a different MCU could likely require approval - since the method they generate the internal clocks are likely to be different. But I again, it would be your "call" whether or not to inform the agency.

[dhouston]

Well, if it happens it will involve about 50 total keyfobs (at least, initially) that will be deployed in a mountain valley (in the Flagstaff area) where cell phones are useless. Given the terrain and the fact that they will be activated only in a medical emergency, I doubt there will be any significant interference issues but the potential for FCC problems is one more thing to consider. They have introduced one new condition that may force me to withdraw anyway.

I had a radiotelephone license about 50 years ago when I finished USAF electronics training but never worked in the field and have never done anything that required approval. It sounds as if you are active with current FCC contact but I doubt many people would find it necessary to seek approval for this.

And, yes, it is a 12V battery. Most remotes like this and even wireless doorbells use a high capacity 12V battery.

There is one other possibility. I might be able to provide a replacement MCU (perhaps of the same type) for the receiver/dialer unit. I'll have to borrow one of theirs to see what that would involve.

[Demon]

Keep in mind I know totally nothing about FCC and other certifications (but want to learn since it will eventually concern me).

What if you use low voltage micros on a new PCB, does that do a difference? I figure the FCC is mainly concerned with interference with other devices, so what if you kept broadcast power down to a minimum. The device is only used around the house right? Or are you expected to have a 300foot range around the house?

Robert

[dhouston]

Keep in mind I know totally nothing about FCC and other certifications

I already knew that. I was responding to languer.

Read the FCC Part 15 Regulations. They spell out in great detail what is acceptable along with test procedures. A friend with more recent experience as a radio engineer tells me enforcement has been very lax for the past 15-20 years as budget cuts have left them with fewer people.

[languer]

For unintentional radiators you want to try and shove yourself (I think) into "§15.103: Exempted devices". In my experience we mostly work with "digital device utilized exclusively in any transportation vehicle including motor vehicles and aircraft". However, the "certificate of conformity" comes in the form of a slew of regulatory tests not required for FCC, but required for a different agency.

Looks like the stuff you're doing is not commercial (i.e. you're not making money or commercializing it), and may perhaps fall under "§15.23: Home-built devices" if you claim that each one you modify is unique in of by itself.

I have not worked creating part-15 devices outside my normal work (where we normally are exempt because of all the additional regulatory testing done anyways); but I'm always interested in hearing how other people approach it.

Link to a USB hub declaration of conformity example: http://cache-www.belkin.com/support/dl/f5u111.pdf

A couple of useful links:
http://www.arrl.org/part-15-radio-frequency-devices (look into the Verification section)
http://www.part15.us/ (a place for questions)
http://transition.fcc.gov/Bureaus/En...2/oet62rev.pdf (short brief from FCC)

[dhouston]

Thanks.

I've used the home-built exception for some kits I designed and a grandson sold several years ago but, in this case, I do not want to put these volunteers cross-wise with the FCC so I'm going to tell them I don't think we should proceed and recommend they spend their funds on some $100 (probably less in volume and even less if there are tax advantages for the manufacturer) units that will dial 911 + 4 other numbers. Perhaps they can use the pendant-less units for spares.