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Pierre_

Issue with a 633

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Hello,

This is my first post here, and I am french, so sorry if it's not really clear, and please ask me if it's not. :P

I am trying to use a 633 TX and a 625 RX. It's not working (of course :lol: ) and I have some questions :

- I use a 317 to provide the 3.3V supply to the 633, fed by a 6V supply able to give 1A. With no load, the output of the 317 is 3.3, but with the 633 connected, It falls to 2.2v. Normal ? (To me it's not, the 317 should maintain the voltage but I don't see what wrong with the wiring so maybe something that I havent understood...)

- Before I applied the power for the first time, but after having solder the SMA connector directly to the 633 case, the Ohm value (bad english sorry) between the video input and the ground is 0. Again, normal ?

- Can I live the channel selection pin to the air on the 633 and the 625 (I don't want to change the channel later, as I am sure to be alone) ?

If you have any questions, or checks to suggest, you are welcome !!

Thanks,

Pierre

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2.2v is not normal and 0 ohms is not normal.

Can you supply pictures and maybe diagram of how you connected your regulator ?

Terry

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Along with Terry's comments ...

I use a 317 to provide the 3.3V supply to the 633, fed by a 6V supply able to give 1A. With no load, the output of the 317 is 3.3, but with the 633 connected, It falls to 2.2v.

That works out to be about 1.5 watts of heat. So, besides the chance of a wiring problem, the VReg would be prone to get too hot (and shut down) if you don't have an adequate heatsink on it.

Before I applied the power for the first time, but after having solder the SMA connector directly to the 633 case, the Ohm value between the video input and the ground is 0.

I measure ~46 ohms on the Video Input. RF output is open circuit.

Can I leave the channel selection pin to the air on the 633 and the 625 (I don't want to change the channel later, as I am sure to be alone) ?

The 633Tx will default to CH-4. The 625Rx does not default, so you will need to ground its CH-4 input.

Can you supply pictures and maybe diagram of how you connected your regulator ?

I agree. This is usually the best way to help us troubleshoot these problems.

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Hello,

Thank you for your answer, they are helping. Seems that I have to order a new 633, and work on my power supply.

I can't supply picture, but here's my 317 diagram. The resistor values that I gave are ball park figure, as I have fine tune one of the resistor to obtain 3,3V on the output.

One thing is the 317 stay cool when I connect the 633, and the voltage in entry does not go down. I am not able to monitor the intensity (my meter only goes to 200 mA).

Thanks,

Pierre

post-6-1190670138_thumb.jpg

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One thing is the 317 stay cool when I connect the 633, and the voltage in entry does not go down.

That sort of implies that the LM317 is not wired correctly. Time to post close up photos of your project.

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That sort of implies that the LM317 is not wired correctly. Time to post close up photos of your project.

I don't have a camera. I have to borrow one, and as it's made on a a test board, it's not really easy to see something. The diagram of the 317 is ok, or am I wrong ? (I know that it's pretty simple, and I checked it several times, but...)

I am going to put a load on my 317 with some resistor to check that it can output 600 mA and find a heatsink to mount on it. I will let you know how it behaves. I have to buy some parts (a 5 Ohm resistor able to take 2 W :blink: and the heatsink for the 317).

I don't understand how I messed up the video entry of the 633, I heated it when I soldered the SMA connector directly on it (as read on the forum), and it was hot, but I was still able to touch it.

Pierre

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The diagram of the 317 is ok, or am I wrong ?

When I calc the voltage using the part values you installed, the Vreg output appears to be under 2V.

I don't understand how I messed up the video entry of the 633 ...

It would be best to show closeup photos of your work. Also, maybe your DVM does not have the resolution to measure low ohm values. The 633's video input is under 50 ohms.

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I know it's a pain in the neck to post close up photo's but with no photo's we don't have much hope of knowing what is wrong with your circuit.

2 x 10ohm resistor will give you 5 ohms but even 1 10 ohm resistor will be ok to see if your 317 is working correctly.

Terry

Edited by Terry

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When I calc the voltage using the part values you installed, the Vreg output appears to be under 2V.

It would be best to show closeup photos of your work. Also, maybe your DVM does not have the resolution to measure low ohm values. The 633's video input is under 50 ohms.

Hello,

Thank you to you 2.

Terry, I have just bought a resistor of 4.7 Ohm and 2 W (big thing), a heat sink (17°C/W) and a new 317 (Mr RC-Cam you are right, the value of the resistor are not correct ?!? I don't understand...). Tonight (1 PM here right now) I will solder a new power supply.

Sorry about the picture, if it's still not working, I'll find/buy a camera.

Regarding the video input, I'll check that again, I was using the "diod test" position of my DVM maybe it rings below 50 Ohm.

Pierre

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please read the datasheet of LM317

then you will see the resistor values to set the voltage is WAY to hi !

that is also why it dont work,

you must also add capacitors in the input, and the output cap

I suggest 100nF and 100uF inparallen BOTH on the input and output,

and locate them as close as possible to your regulator and resistors,

keep it all with SHORT wires.

mound a 3x3 cm 1mm thick aluminium

plate on the regulator, if it gets hotter than you can hold your fingers on it,

when it is driving your Airwave unit

Edited by ThomasScherrer

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I was using the "diode test" position of my DVM

The diode position on most meters reads the voltage across a forward conducting silicon junction. In this case, you should use the ohmmeter to measure resistance.

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Hello,

Some news.

The 317 is working. I have downloaded another version of the 317 datasheet, and I have found a typical value for R1 of 240 Ohm. I was way out. Thanks Thomas for this, I wasn't able to find a typical value in the fairchild datasheet, so I took big resistor to have a low current through them. I have add 100nF cap on the entry and output. Not sure about the 100uF, because I have a 470uF on the output as specified on the 633 datasheet, and the 317 datasheet only suggest a 100nF on the entry ?

Right now I have a 4,7 Ohm 2W resistor to simulate the 633 and after 10 minutes, the heatsink mounted on the 317 is hot, but I can hold my finger on it, and the voltage is around 3.26 V. Seems fine.

I have checked the value between the video input and the ground on a low scale of my DVM, and it's around 45 Ohm....

Things are going way better. Thank you very much to you all for the support !

So next step is wiring again the 633, put the channel 4 of the 625 to the earth and try it.

I will let you know how it goes.

Pierre

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Hello,

The news. I have wire the 633 on the new power supply, and ground the ch4 on the 625.

I just have transmitted sound !!!

Thanks you guys very much for your help !

I need to wire the video signal now. I have a amplitude issue, and I need to understand how to lower the voltage from the cam. I have spotted a good thread on that.

Pierre

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Hello,

Some news, I have tried with video and I am quite disapointed by the noise added :

First video

I have check the Vp-p out of my camera on a 75 ohm resistor, and I have 2V with a light pointing on the lens. Can this cause this kind of noise ?

I wasn't able to find on the forum a way to lower the Vp-p of the cam. Can I use 2 resistors to split the voltage in 2 is the good solution, or is there a better way ?

Thanks for your help !

Pierre

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The noise looks to me like you don't have the Rx and Tx set to the same channel. It is what I would expect if the channels were off by one position. Otherwise, verify proper supply voltages on the Rx and Tx. Or, is there any chance you have a short on the Tx's or Rx's antenna input?

In regards to the 2Vpk-pk video, that is definately wrong. It will cause very washed out video, poor contrast, and other issues. You mentioned that you are measuring the level directly out of the CMOS video camera. Let's try another way just as a sanity test. With the video camera connected only to the Tx, what is the bright white's Vpk-pk video level at the video input of the Airwave Tx? Do not install a resistor for this (the Airwave module has one in it).

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Thanks for you answer.

The noise looks to me like you don't have the Rx and Tx set to the same channel.

I have grounded the channel 4 of the 625 and haven't modify the 633.

Otherwise, verify proper supply voltages on the Rx and Tx.

Seems fine on a DVM. Should I check with the oscope?

Or, is there any chance you have a short on the Tx's or Rx's antenna input?

On the TX and RX, the resistance value between the antenna pin and the ground is above 20 MOhm.

In regards to the 2Vpk-pk video, that is definately wrong. It will cause very washed out video, poor contrast, and other issues. You mentioned that you are measuring the level directly out of the CMOS video camera. Let's try another way just as a sanity test. With the video camera connected only to the Tx, what is the bright white's Vpk-pk video level at the video input of the Airwave Tx? Do not install a resistor for this (the Airwave module has one in it).

The value is now just below 1 Vpk-pk ?! ?

Should I try to ground another channel on the 625 and 633 ?

Pierre

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Should I try to ground another channel on the 625 and 633 ?

It would be wise to setup the Tx and Rx so that you can try all the RF channels.

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Hello,

Some news !! I finally have found the source of my parasites. They came from the 625RX power supply. I am using a cheap AC 230V/DC 6V regulator. If I use a 2S lipo to feed my 7805, it works fine, but with the régulator, I have lines on the video :

http://www.dailymotion.com/Pierre__/video/5555027

I have the same regulator on the 633TX, with no pb. But if I use it on the 7805 of the 625RX...

So far I have 2 100nF capacitors on the 7805. Any ideas of values for capacitor that would cure this issues, as I would like to use this regulator on the RX side.

Thanks,

Pierre

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If I use a 2S lipo to feed my 7805, it works fine, but with the régulator, I have lines on the video

The 7805 is not a good choice for 2S LiPO voltage. You need a LDO, like the LM2940 (or something similar). Capacitor choice is important -- follow the data sheet very carefully.

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Hi,

In fact I don't want to use a lipo 2S, I would like to use the AC 220V reg, as the RX would be near a house (the one that is not working).

I have tried with the capacitor I have. I will buy 0,33uF and try again with the reg.

The result is almost perfect with the lipo, I like that ! :D

Pierre

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I am using a cheap AC 230V/DC 6V regulator. If I use a 2S lipo to feed my 7805, it works fine, but with the régulator, I have lines on the video

6V is too low to feed a 7805. It needs at least 1.5V difference between input and output to regulate effectively. As Mr. RC-Cam said, there are similar parts that require a lower voltage difference. I don't know what you're using on the 633, but as the output is 3.3V the difference is greater anyway.

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In fact I don't want to use a lipo 2S, I would like to use the AC 220V reg, as the RX would be near a house (the one that is not working). I have tried with the capacitor I have. I will buy 0,33uF and try again with the reg.

Supply filtering on most A/C wall adapters is inadequate. They are often 1/2 wave rectified which results in very large ripple. If you are going to use a wall adapter to power the Rx's 5VDC supply, then use a 9VDC / 500mA+ rated version and add a 2200uF cap to it. You can use your 7805 VReg IC with that.

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Supply filtering on most A/C wall adapters is inadequate. They are often 1/2 wave rectified which results in very large ripple. If you are going to use a wall adapter to power the Rx's 5VDC supply, then use a 9VDC / 500mA+ rated version and add a 2200uF cap to it. You can use your 7805 VReg IC with that.

Hello,

Thank you for the answers. You were right, with an 7.5 A/C wall adapter, the video is just fine !!

Thank you very much to all again for all you help !!!

Pierre

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