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JP1 Remotes
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cauer29
Joined: 03 Feb 2010
Posts: 236
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 Posted: Mon Dec 13, 2010 1:47 am Post subject: |
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| tpaxadpom wrote: | A,A, this is very informative post. I took jp1.3 interface, RS232 cable to my mom's place. I found 10k and 7+k resistors and ran the test. When I connected the battery I just saw some garbage in the receive window. So my interface failed the test. At this point I should probably buy new components (at the very least transistors in TO-92 package) and start from scratch. 
I bought 2 15-100 for $2.97 at Radio Shack. I thought it was price mistake but the sales clerk told me it wasn't. I bought one then called other stores and found another one. So I have one spare remote. Though I hope the first one is going to cooperate once I fix interface issues.
It would be very helpful if someone could measure Vbe and Vce voltages on their inferface when it is plugged into PC. |
Ok, with the interface cable not connected to the remote, but connected to the PC comm port, you will see ~-0.6V on the base of Q1. The collector of Q1 will show not much voltage since the R1 pullup resistor is not getting any voltage from the remote. If it is connected to the remote, then the collector of Q1 will be at ~3V and it will toggle between 3V and ground as the PC comm port's Tx line sends data. You will need a 'scope to see that, unless you can set the baud rate to an extremely low rate (20 bps or less). Setting and clearing RTS on the com test program, will cause the base of Q2 to toggle between -0.6V and +0.6V. When it's +0.6V, the collector of Q2 will be within 50mv of ground. With RTS on in the com test program and the cable connected to the remote, the collector of Q2 will be near ground and at ~3V when RTS is off. When RTS goes off, you should get 2 flashes on the remote's LED. With DTR on in the com test program, the collector of Q3 will be within ~50mv of ground unless the remote is actually sending something, at which time, it will toggle back and forth between ground and ~7V. The exact voltage will depend on the particular design of the PC's comm port. Some will be as high as +12V while some others may be as low as 4V. Anything in that range should be fine. If the JP1.x cable is not connected to the remote, the collector of Q3 should be in the 4 to 12 volt range. With the remote connected but not sending anything, it should be near ground. The base of Q3 will sit at ~0.6V when connected to the remote if it's not sending anything and toggle between ground and 0.6V as the remote sends data.
A.A. |
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tpaxadpom
Joined: 19 Sep 2007
Posts: 64
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| Posted: Mon Dec 13, 2010 11:12 pm Post subject: |
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| cauer29 wrote: | Ok, with the interface cable not connected to the remote, but connected to the PC comm port, you will see ~-0.6V on the base of Q1. The collector of Q1 will show not much voltage since the R1 pullup resistor is not getting any voltage from the remote. If it is connected to the remote, then the collector of Q1 will be at ~3V and it will toggle between 3V and ground as the PC comm port's Tx line sends data. You will need a 'scope to see that, unless you can set the baud rate to an extremely low rate (20 bps or less). Setting and clearing RTS on the com test program, will cause the base of Q2 to toggle between -0.6V and +0.6V. When it's +0.6V, the collector of Q2 will be within 50mv of ground. With RTS on in the com test program and the cable connected to the remote, the collector of Q2 will be near ground and at ~3V when RTS is off. When RTS goes off, you should get 2 flashes on the remote's LED. With DTR on in the com test program, the collector of Q3 will be within ~50mv of ground unless the remote is actually sending something, at which time, it will toggle back and forth between ground and ~7V. The exact voltage will depend on the particular design of the PC's comm port. Some will be as high as +12V while some others may be as low as 4V. Anything in that range should be fine. If the JP1.x cable is not connected to the remote, the collector of Q3 should be in the 4 to 12 volt range. With the remote connected but not sending anything, it should be near ground. The base of Q3 will sit at ~0.6V when connected to the remote if it's not sending anything and toggle between ground and 0.6V as the remote sends data.
A.A. |
I really aprpeciate it A.A. I figure out the problem really fast following your guidelines. I read your reply when I was at work. I didn't have the remote with me but I had Jp1.3 cable. I knew that the problem was likely with Q1. Q2 wasn't an issue as I was able to reset the remote via RTS line using com port program. Also I was getting some garbage messages on the serial port when I was doing a loop back test with 9V battery. So Q3 seem to work fine as well. I did a quick check without the remote control attached to the interface and everything looked fine. Then I connected pin 1 and pin 3 on the remote control side to external PSU and set it to 5V. I didn't see Vc toggling as I was typing in the control panel of com test program. Then I probe around the transistor on the pins and discovered that Vce wasn't 5V. Since I've used SOT23 transistors it was impossible to see this. Anyhow I'm up and running with your great help.
Note: According to Tommy's troubleshooting guide, interface should work even with the old 9V battery as long as the voltage is above 3V. Well I decided to play with external PSU to see how low I can get Vce before Q1 stops switching. Well it worked fine at 1.5V and was intermittent at 1.3V. Basically I wasn't seeing all the characters I was typing and saw some garbaghe on the serial port. Obviously this voltage will vary from transistor to transistor, but I decided to share this in case someone wants to run a simple test and doesn't have 9V handy. |
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cauer29
Joined: 03 Feb 2010
Posts: 236
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| Posted: Mon Dec 13, 2010 11:27 pm Post subject: |
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| tpaxadpom wrote: | I really aprpeciate it A.A. I figure out the problem really fast following your guidelines. I read your reply when I was at work. I didn't have the remote with me but I had Jp1.3 cable. I knew that the problem was likely with Q1. Q2 wasn't an issue as I was able to reset the remote via RTS line using com port program. Also I was getting some garbage messages on the serial port when I was doing a loop back test with 9V battery. So Q3 seem to work fine as well. I did a quick check without the remote control attached to the interface and everything looked fine. Then I connected pin 1 and pin 3 on the remote control side to external PSU and set it to 5V. I didn't see Vc toggling as I was typing in the control panel of com test program. Then I probe around the transistor on the pins and discovered that Vce wasn't 5V. Since I've used SOT23 transistors it was impossible to see this. Anyhow I'm up and running with your great help.
Note: According to Tommy's troubleshooting guide, interface should work even with the old 9V battery as long as the voltage is above 3V. Well I decided to play with external PSU to see how low I can get Vce before Q1 stops switching. Well it worked fine at 1.5V and was intermittent at 1.3V. Basically I wasn't seeing all the characters I was typing and saw some garbaghe on the serial port. Obviously this voltage will vary from transistor to transistor, but I decided to share this in case someone wants to run a simple test and doesn't have 9V handy. |
Glad to see that you got it working. I think somebody or other made a version of the JP1.x cable using so-called "digital" transistors. Those are transistors with a built-in resistor in series with the base and a built-in emitter to base resistor. The next time I have to build a JP1.x, I'm going to go that route, since it greatly reduces the component count.
As for the battery voltage, I expect that Tommy Tyler said to use a 9V battery because although a single AA would work if it had sufficient charge left in it, the 9V battery is a bit easier to deal with because it has both terminals on one end. An AA cell would be too much to juggle and there would always be the question of whether the cell had enough charge.
A.A. |
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tpaxadpom
Joined: 19 Sep 2007
Posts: 64
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| Posted: Tue Dec 14, 2010 2:34 am Post subject: |
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I agree, 9V is a safer bet, plus if one builds the cable per his recipe one person can run the test without someone assisting. I thought it would look cleaner and better not to have any exposed contacts on JP1.3 interface cable inside the remote.
I'm going to replace RS232 gender on my cable and solder thinner cables (currently I have 5 24AWG cables inside my remote that won't let the back cover close all the way). There is still a lot of work left and I need to mod my other remote. |
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