Leon, I'm not sure if the delivery guy would willingly submit to being placed in "timeout." Or did you mean timeout in another sense. I'm not just giving you a hard time; I would like to know what part the solutions being discussed would benefit from a timeout.
I have two Propeller communicating wireless I use everyday for data collecting. The transmitting Prop includes an incrementing byte after the address header so the receiving Prop knows whether it's new information or a retransmission of the last data received. While the receiving Prop doesn't record the retransmitted data it does send another acknowledgment (ack). The Tx Prop will repeat the send up to 32 times with increasing waits for an ack. There are plenty of times all 32 attempts are made without an ack being received. More than half the time the problem isn't that the Rx Prop didn't receive the transmission but that the Tx Prop didn't receive the acknowledgment. I plan on changing the code so the Tx Prop hangs on to the data and retries a little later and only after repeated and prolonged attempts to communicate with the other Prop is an error given. As it is now the error messages are occasionally disruptive and if the Tx Prop had just waited and tried again the communication problem could have been resolved without human intervention (as it is now, I need to resend the data).
Since Microcontroller's device only gets new data once a day, I think smbaker's idea of sending the button count an excellent idea. If I were the one making this thing, I think I'd do just that. (Just because I say it's the way I'd do it doesn't mean I think any other way is wrong.)
Leon, sorry for being a smart aleck. I couldn't resist the play on words.
In case it's not a worldwide term. Timeout is what parents give their missbehaving children by having them sit in a chair by themselfs (often in a corner of a public room or in the child's bedroom). It's about the same as being "sent to your room" when I was a kid.
The FeDex delivery truck has a 2-way radio system installed
that is always on. If you have a scanner you could set it
to receive the signal put out by the local oscillator of its receiver
and this would act as a signal that the delivery truck is outside.
You need to find out the frequency though...and then look 10.7
mhz up or down. The radio may be some sort of system that looks
for an open frequency in a group of channels so you might have to
scan a range or a group of channels to detect the truck. I worked
on a security project once at my last job that used this trick to
take images when a specific type of device was nearby...it worked
very well, it was a sneaky project and a lot of fun to work on. I don't
know very much about the various types of receivers but the ones
we were interested in were very easy to detect. Most people carrying
a receiving device are unaware that they transmit a weak signal all the time.
The ones we detected generated an rf signal about 10mhz above the
frequency it was set to receive data on.
@Microcontrolled
I think the best bet is to come up with some useful Prop
based gadgets and sell them on ebay. You are a really smart
kid and I bet you could think of something :-)
I was referring to smbaker's post about problems with ACK. A timeout could be a solution. Your technique of counting the number of retries amounts to the same thing.
You could put an element in the corner of the display, resembling a red/green led, with a lable 'in range' to show that the xbees are communicating. that would, to me, be simple and effective to show that the xbees are in range and communicating. im not sure about the one minute 'com ping', if it was me i would go with like a 10 or 15 second com status. but thats just me. i think you're doing a great job and hope you get more!
Microcontrolled, Do you know if there is a FCC regulation about how frequently you can transmit data? On page 35 of the July 2010 Nuts & Volts (this same issue has a great article about using a Propeller to make a RFID lock box) in the wireless tail light article it says "To keep in compliance with FCC regulations, the 'lights are on' signal only transmits once every 10 seconds when lights are turned on." Is this something you need to worry about?
I know you've gotten a lot of ideas sent your way. The only one I've given that I think is very important was about not making the driver press the button more than once.
I still have more input to provide which you can ignore and still have a great project. I like sound feed back as well a visual. Piezo speakers are pretty easy to use and are really useful. With the set up have, a piezo makes a friendly bleep with each successful data transmission. If after 32 tries it doesn't get an acknowledgment in makes a bonk sound. I find it very useful.
You could use a piezo with both of your boards. The outside board could provide a friendly sound when the button is pressed. The inside board could also make a friendly sound when the package arrives. A lack of communication error could also be reinforced with an audio error message (just don't make it too annoying). If your interested in adding piezo speakers, I'd be happy to share my schematic and code. I think I've got a couple of friendly beeps, deebeeps and blips figured out.
I looked through your schematic. I'm curious where you got your relay/transistor circuit. I have several Propellers controlling relays and the circuits I've seen use NPN transistors. I'm no transistor expert so I don't know if it's better to use a NPN or a PNP like you show. All the relay/transistor circuits I've seen also have a resistor between the microcontroller and the base pin of the transistor. Can you measure the current to the base pin to make sure it's not excessive? I have a 470 ohm resistor in the circuits I use. Maybe a PNP doesn't need one. I don't know but want to make sure you know what your doing here.
You will want add a Vdd connection to your EEPROM when you're ready to finalize your schematic.
I spend a lot of my day improving circuits I use in my lab. It's fun. I often don't know if I'm "working" or "playing" because my work is also my hobby.
@Duane:I was using the NPN relay circuit, but since the relay will be on most of the time I changed to PNP to resist current draw on the chip. I've never seen it done, but it works so it may just be the next great idea or a bad way to fry my Propeller. As you probably know, an NPN transistor allows current to flow from the collector to emitter when the base is logic high. A PNP does the opposite, allowing current to only flow between the collector and emitter when the base is logic low. This means the Propeller will not have to continuously pull this pin high, which in theory releases stress on the chip.
Also, I will be sure to fix the schematic for the final version, thanks for catching that. :-)
Oh, and I don't know if you knew this or not, but I wrote that N&V article on the RFID box!!
@Everyone: THANKS for the suggestions, just FYI, I do have a timeout on the communications, I didn't before realize that the FedEx guy wouldn't care to press it again, but since it was brought to my attention, I will take care of that. You're all right, I need to have a better way of telling when it is in range, and I will make sure I get the button transmitting endlessly until the ACK byte is returned. Once this is complete, it should be a flawless system.
Since I have a 5-pos switch on the side of the device, I might as well use all 5 positions and include a drop down menu with things like: "Display Seconds: On" and "Show connection status: On"
This will be the most versitile way to get this working correctly.
Microcontrolled, Your PNP transistor might be the next great idea. Is Parallax really going to have the monitor on more than 12 hours a day? Wow. I still wonder if there should be a resistor between the Prop and the transistor. Do you have a volt meter? I'd use a 1ohm resistor and measure the voltage drop to make sure your not pull too much current from the Prop to turn the relay off.
Do you know about latching relays? I think this is perfect application for one. A latching relay only needs power to change states. Once it's on it doesn't take any current to keep it on and the same goes for turning it off. I purchased some in my last Digi-Key order, but I haven't tried them yet. Here's a link to the one I chose. Do you have time to modify your design to include one? If you want, and there's time, I'll drop one in the mail to you (Just PM me your address). The monitor doesn't pull more than 2 amps does it? (The relay is rated 2A @ 30V.)
It doesn't have to pull HIGH to turn off, it just has to be left floating. And even if it is high, no current it being pulled. I don't guess it would hurt to attach the resistor, though.
Microcontrolled, Do you know if there is a FCC regulation about how frequently you can transmit data? On page 35 of the July 2010 Nuts & Volts (this same issue has a great article about using a Propeller to make a RFID lock box) in the wireless tail light article it says "To keep in compliance with FCC regulations, the 'lights are on' signal only transmits once every 10 seconds when lights are turned on." Is this something you need to worry about?
The modules used in the N&V article were 433 Mhz linx modules, and the linx datasheet states that the modules are not FCC-approved and may require the user to get FCC approval prior to selling or operating the device. The 2.4Ghz XBee modules on the other hand do appear to be FCC approved. According to Appendix A of the XBee manual, there are some requirements concerning labeling and the types of antennas that can be used, but I don't see anything in there about maximum data rates.
All goes well, the system works great, here is some of the documentation attached.
I've also attached some pictures so you can see what this looks like right now. As you can see in the pics, I have an RCA connector on the board. This is mostly for debugging, but it can also be handy as an external output.
I'd suggest (surprise, surprise), you use some thin cable ties to route the wire in the outside case. It would make the setup look even nicer. You want people who see this to want to hire you to do similar projects. My brother who's in advertizing says most purchase decisions are based more on emotion than logic. You want potential customers (myself included) to have a strong positive emotional response when they see the final pictures. I also don't like to see wire running near a chip antenna. I use several transceivers (2.5GHz) with chip antennas I think they can be kind of picky about obstructions (people, and metal).
Also a note about heat shrink tubing. Everyone loves heat shrink tubing right? I do. After reading NASA's best practices in electronics and learning they require transparent or at least translucent heat shrink tubing I switched to transparent tubing for my own use. I've been very glad I a have. It's so nice to be able to still see the connection and anything else that would be hidden under opaque tubing. I don't think you need to replace the heat shrink tubing on this project, but think about it next time you buy some.
Have you decided on the button for the outside board? Make it relatively big and very easy to reach (you've read everyone's comments about delivery men rushing through their work). I'm guessing the button isn't going to be mounted directly on the enclosure. You ought to make sure the wires coming out of the enclosure can survive some pretty abusive tugs.
The enclosures are really nice. I'm going to see if I can use some acrylic I have to make an enclosure. I doubt mine will look as nice as these.
Congratulations on another great project (yeah, I did know you wrote the N&V article, way cool!). You ought to write up this experience and submit it (with Key's okay, though another article about Parallax products could only be a good thing for him and Parallax). It's a pretty unique experience for someone in general and even more so for someone your age.
Do we get to see the final code in the Completed Projects Forum?
@Duane: Thanks! About the wires in the outside case, you don't have to worry about the wires being wrapped or away from the anntenna, because those are only temporary wires until I deside upon a pushbutton. Unfortunatly I can't use a nice, large pushbutton (I've found the larger the drillbit, the messier the hole) but a small one will still look nice if done correctly and selected properly. Once I get a pushbutton, it will connect to the header block with a 2 pin male header and the wires will be shrink wrapped. Also, I don't think transparent shrink wrap would look right for me because I shrink it with my soldering iron, which leaves black marks on the plastic.
@KaosKidd: Welcome to the forum and thank you very much!!
@Luis Digital: I discussed this a while ago, but I went with the PNP transistor because it doesn't pull current when the relay is active while the NPN circuit does. A PNP is opposite an NPN. Whereas an NPN transistor allows current flow when the base it high, a PNP allows current flow when the base is pulled low. This way, the Propeller can simply pull the pin low with little to no current draw while the relay is latched, and pull it high to disactivate the relay. Even when it is pulled high, little or no current is pulled.
The Propeller Proto Boards have 10K pull-ups on both the data and the clock of the EEPROM. (The Demo Board only pulls the data line high.)
You have pins 5 and 6 of the Propeller chip routed to "VSS" and all other connections to ground are labeled "GND." It would be better to be consistent in your labels. (It also looks funny for the line to turn up to "VSS." Schematics usually (if not always) have lines turn down to reach ground.) It also would look better, and more "professional" (this is a professional job, right?) to connect all VDDs and VSSs of the Propeller chip.
I'd name the specific EEPROM chip (AT24C512). I'd also suggest naming the RTC chip and its crystal's frequency.
Is VCC of the RTC and the VCC or the monitor power the same? I'd be surprised if they were. I'd suggest you use the voltage each uses instead of VCC.
It would be nice if you could identify the diode more specifically than "Standard 12V diode" in your receiver bill of materials.
I see I'm not the only one puzzled by your choice of transistor. I don't think I have a 2N3906 transistor but I'll think I'll try out your method using some other PNP I have on hand.
You can also get stepped reamers which are good for large holes. For thin ali and steel plate I use punches which you tighten with a spanner and an allen key.
@Luis Digital: I discussed this a while ago, but I went with the PNP transistor because it doesn't pull current when the relay is active while the NPN circuit does. A PNP is opposite an NPN. Whereas an NPN transistor allows current flow when the base it high, a PNP allows current flow when the base is pulled low. This way, the Propeller can simply pull the pin low with little to no current draw while the relay is latched, and pull it high to disactivate the relay. Even when it is pulled high, little or no current is pulled.
The circuit will not work: There is no current flow between emitter and collector.
If you want to use a PNP transistor, the collector should be placed on the negative, and the emitter in the relay.
Edit:
Another thing: yes there is current flow in the base, from emitter to base. So for some cases is very convenient to use a resistor in the base (1k for example).
I'm guessing Microcontrolled has his circuit already wired up and is able to activate the relay. I think the problem is he switched the transistor symbol around on his schematic.
Luis is right that as the circuit is described in the schematic, it wouldn't work.
The lack of a resistor on the base bothers me too. The Propeller might not be sourcing any current but it must be sinking some
I just checked the transistor. It is a PNP and I was mistaken about the exact part number, it is a 2N4403. Still, the emitter IS to ground, the collector IS to the coil, and the circuit DOES work.
The reason why I used a PNP in the first place is because I don't have any NPN's. I had one set apart for this project but I found that it was not working. Then I thought, "Why not swipe it out for a PNP?" so I did, and I found many advantages to it. As long as it continues working, that is what I am going to use. I did place an order for more NPNs last night but they won't arrive for 7-16 days.
Comments
I have two Propeller communicating wireless I use everyday for data collecting. The transmitting Prop includes an incrementing byte after the address header so the receiving Prop knows whether it's new information or a retransmission of the last data received. While the receiving Prop doesn't record the retransmitted data it does send another acknowledgment (ack). The Tx Prop will repeat the send up to 32 times with increasing waits for an ack. There are plenty of times all 32 attempts are made without an ack being received. More than half the time the problem isn't that the Rx Prop didn't receive the transmission but that the Tx Prop didn't receive the acknowledgment. I plan on changing the code so the Tx Prop hangs on to the data and retries a little later and only after repeated and prolonged attempts to communicate with the other Prop is an error given. As it is now the error messages are occasionally disruptive and if the Tx Prop had just waited and tried again the communication problem could have been resolved without human intervention (as it is now, I need to resend the data).
Since Microcontroller's device only gets new data once a day, I think smbaker's idea of sending the button count an excellent idea. If I were the one making this thing, I think I'd do just that. (Just because I say it's the way I'd do it doesn't mean I think any other way is wrong.)
Leon, sorry for being a smart aleck. I couldn't resist the play on words.
In case it's not a worldwide term. Timeout is what parents give their missbehaving children by having them sit in a chair by themselfs (often in a corner of a public room or in the child's bedroom). It's about the same as being "sent to your room" when I was a kid.
Duane
The FeDex delivery truck has a 2-way radio system installed
that is always on. If you have a scanner you could set it
to receive the signal put out by the local oscillator of its receiver
and this would act as a signal that the delivery truck is outside.
You need to find out the frequency though...and then look 10.7
mhz up or down. The radio may be some sort of system that looks
for an open frequency in a group of channels so you might have to
scan a range or a group of channels to detect the truck. I worked
on a security project once at my last job that used this trick to
take images when a specific type of device was nearby...it worked
very well, it was a sneaky project and a lot of fun to work on. I don't
know very much about the various types of receivers but the ones
we were interested in were very easy to detect. Most people carrying
a receiving device are unaware that they transmit a weak signal all the time.
The ones we detected generated an rf signal about 10mhz above the
frequency it was set to receive data on.
@Microcontrolled
I think the best bet is to come up with some useful Prop
based gadgets and sell them on ebay. You are a really smart
kid and I bet you could think of something :-)
I was referring to smbaker's post about problems with ACK. A timeout could be a solution. Your technique of counting the number of retries amounts to the same thing.
I know you've gotten a lot of ideas sent your way. The only one I've given that I think is very important was about not making the driver press the button more than once.
I still have more input to provide which you can ignore and still have a great project. I like sound feed back as well a visual. Piezo speakers are pretty easy to use and are really useful. With the set up have, a piezo makes a friendly bleep with each successful data transmission. If after 32 tries it doesn't get an acknowledgment in makes a bonk sound. I find it very useful.
You could use a piezo with both of your boards. The outside board could provide a friendly sound when the button is pressed. The inside board could also make a friendly sound when the package arrives. A lack of communication error could also be reinforced with an audio error message (just don't make it too annoying). If your interested in adding piezo speakers, I'd be happy to share my schematic and code. I think I've got a couple of friendly beeps, deebeeps and blips figured out.
I looked through your schematic. I'm curious where you got your relay/transistor circuit. I have several Propellers controlling relays and the circuits I've seen use NPN transistors. I'm no transistor expert so I don't know if it's better to use a NPN or a PNP like you show. All the relay/transistor circuits I've seen also have a resistor between the microcontroller and the base pin of the transistor. Can you measure the current to the base pin to make sure it's not excessive? I have a 470 ohm resistor in the circuits I use. Maybe a PNP doesn't need one. I don't know but want to make sure you know what your doing here.
You will want add a Vdd connection to your EEPROM when you're ready to finalize your schematic.
I spend a lot of my day improving circuits I use in my lab. It's fun. I often don't know if I'm "working" or "playing" because my work is also my hobby.
Keep up the good work/play.
Duane
Also, I will be sure to fix the schematic for the final version, thanks for catching that. :-)
Oh, and I don't know if you knew this or not, but I wrote that N&V article on the RFID box!!
@Everyone: THANKS for the suggestions, just FYI, I do have a timeout on the communications, I didn't before realize that the FedEx guy wouldn't care to press it again, but since it was brought to my attention, I will take care of that. You're all right, I need to have a better way of telling when it is in range, and I will make sure I get the button transmitting endlessly until the ACK byte is returned. Once this is complete, it should be a flawless system.
Since I have a 5-pos switch on the side of the device, I might as well use all 5 positions and include a drop down menu with things like: "Display Seconds: On" and "Show connection status: On"
This will be the most versitile way to get this working correctly.
Thanks for the suggestions everybody!!
Do you know about latching relays? I think this is perfect application for one. A latching relay only needs power to change states. Once it's on it doesn't take any current to keep it on and the same goes for turning it off. I purchased some in my last Digi-Key order, but I haven't tried them yet. Here's a link to the one I chose. Do you have time to modify your design to include one? If you want, and there's time, I'll drop one in the mail to you (Just PM me your address). The monitor doesn't pull more than 2 amps does it? (The relay is rated 2A @ 30V.)
The modules used in the N&V article were 433 Mhz linx modules, and the linx datasheet states that the modules are not FCC-approved and may require the user to get FCC approval prior to selling or operating the device. The 2.4Ghz XBee modules on the other hand do appear to be FCC approved. According to Appendix A of the XBee manual, there are some requirements concerning labeling and the types of antennas that can be used, but I don't see anything in there about maximum data rates.
I've also attached some pictures so you can see what this looks like right now. As you can see in the pics, I have an RCA connector on the board. This is mostly for debugging, but it can also be handy as an external output.
Micro, AWESOME job.
KK
I'd suggest (surprise, surprise), you use some thin cable ties to route the wire in the outside case. It would make the setup look even nicer. You want people who see this to want to hire you to do similar projects. My brother who's in advertizing says most purchase decisions are based more on emotion than logic. You want potential customers (myself included) to have a strong positive emotional response when they see the final pictures. I also don't like to see wire running near a chip antenna. I use several transceivers (2.5GHz) with chip antennas I think they can be kind of picky about obstructions (people, and metal).
Also a note about heat shrink tubing. Everyone loves heat shrink tubing right? I do. After reading NASA's best practices in electronics and learning they require transparent or at least translucent heat shrink tubing I switched to transparent tubing for my own use. I've been very glad I a have. It's so nice to be able to still see the connection and anything else that would be hidden under opaque tubing. I don't think you need to replace the heat shrink tubing on this project, but think about it next time you buy some.
Have you decided on the button for the outside board? Make it relatively big and very easy to reach (you've read everyone's comments about delivery men rushing through their work). I'm guessing the button isn't going to be mounted directly on the enclosure. You ought to make sure the wires coming out of the enclosure can survive some pretty abusive tugs.
The enclosures are really nice. I'm going to see if I can use some acrylic I have to make an enclosure. I doubt mine will look as nice as these.
Congratulations on another great project (yeah, I did know you wrote the N&V article, way cool!). You ought to write up this experience and submit it (with Key's okay, though another article about Parallax products could only be a good thing for him and Parallax). It's a pretty unique experience for someone in general and even more so for someone your age.
Do we get to see the final code in the Completed Projects Forum?
Duane
Good work! I can't wait to press that button!
@KaosKidd: Welcome to the forum and thank you very much!!
You could make a capacitive sensor with tinfoil then no holes are needed.
Documented, commented, all pins in constants and all variables labeled!
The transistor (Q1) is never going to conduct electricity, because you drew a PNP type, the correct picture is NPN.
@Microcontrolled: Looking great! Nice work.
A couple of nit picks about your schematics.
The Propeller Proto Boards have 10K pull-ups on both the data and the clock of the EEPROM. (The Demo Board only pulls the data line high.)
You have pins 5 and 6 of the Propeller chip routed to "VSS" and all other connections to ground are labeled "GND." It would be better to be consistent in your labels. (It also looks funny for the line to turn up to "VSS." Schematics usually (if not always) have lines turn down to reach ground.) It also would look better, and more "professional" (this is a professional job, right?) to connect all VDDs and VSSs of the Propeller chip.
I'd name the specific EEPROM chip (AT24C512). I'd also suggest naming the RTC chip and its crystal's frequency.
Is VCC of the RTC and the VCC or the monitor power the same? I'd be surprised if they were. I'd suggest you use the voltage each uses instead of VCC.
It would be nice if you could identify the diode more specifically than "Standard 12V diode" in your receiver bill of materials.
I see I'm not the only one puzzled by your choice of transistor. I don't think I have a 2N3906 transistor but I'll think I'll try out your method using some other PNP I have on hand.
I still think this is a really nice project.
Duane
http://www.rapidonline.com/Tools-Fasteners-Production-Equipment/Hand-Tools/Punches-Rivets/Circular-sheet-metal-punches/34566/kw/86-5310?source=googleps&utm_source=googleps
Graham
The circuit will not work: There is no current flow between emitter and collector.
If you want to use a PNP transistor, the collector should be placed on the negative, and the emitter in the relay.
Edit:
Another thing: yes there is current flow in the base, from emitter to base. So for some cases is very convenient to use a resistor in the base (1k for example).
Luis is right that as the circuit is described in the schematic, it wouldn't work.
The lack of a resistor on the base bothers me too. The Propeller might not be sourcing any current but it must be sinking some
Duane
I don't know how, but it does.