DMX data issue

lready have two USB => DMX dongles that I am trying to use to run the sho w, along with several pieces of DMX gear controlled by the dongles. I just purchased 3 Lynx Express 16 channel DMX dimmers to add to the show. Unfor tunately, they don't like the output from the dongles I am using. After tr oubleshooting with another hobbyist's equipment, we found the output from m y dongles is about 5V - 6V PTP. The output from his dongle is 12V PTP. It appears the Lynx express does not like the lower voltage. Going by the de signer's parts list, the LEs supposedly use Texas Instruments SN65176BP RS-

485 transceivers to handle the RS-485 bus, but when I look at the devices, they actually have STMicroelectronics ST485BN chips installed. I'm wonderi ng if the SN65176BP chips would have better sensitivity, and if I obtained some of them and plugged them in if the devices would start working with th e lower voltage? Does anyone know of another alternative 8 pin DIP RS-485 transceiver which might work with the lower voltages?

I think they're all spec'd to switch at TTL levels. The data sheet for the ST485BN shows Vcc MAX at 7vdc. At Vcc = 5vdc, they're spec'd to switch a t 2vdc. I've used the '176s at VCc=5vdc with no problem. They're might by some input resistors in the LEs causing a drop?

lready have two USB => DMX dongles that I am trying to use to run the sho w, along with several pieces of DMX gear controlled by the dongles. I just purchased 3 Lynx Express 16 channel DMX dimmers to add to the show. Unfor tunately, they don't like the output from the dongles I am using. After tr oubleshooting with another hobbyist's equipment, we found the output from m y dongles is about 5V - 6V PTP. The output from his dongle is 12V PTP. It appears the Lynx express does not like the lower voltage. Going by the de signer's parts list, the LEs supposedly use Texas Instruments SN65176BP RS-

485 transceivers to handle the RS-485 bus, but when I look at the devices, they actually have STMicroelectronics ST485BN chips installed. I'm wonderi ng if the SN65176BP chips would have better sensitivity, and if I obtained some of them and plugged them in if the devices would start working with th e lower voltage? Does anyone know of another alternative 8 pin DIP RS-485 transceiver which might work with the lower voltages?

are the bus three-stated between packets and does one of them has fail-safe bias resistors ?

-Lasse

What OS?

One can write an app in Linux for it.

I think there are some already out there.

Den fredag den 6. februar 2015 kl. 01.23.06 UTC+1 skrev Maynard A. Philbroo k Jr.:

already have two USB => DMX dongles that I am trying to use to run the s how, along with several pieces of DMX gear controlled by the dongles. I ju st purchased 3 Lynx Express 16 channel DMX dimmers to add to the show. Unf ortunately, they don't like the output from the dongles I am using. After troubleshooting with another hobbyist's equipment, we found the output from my dongles is about 5V - 6V

does not like the lower voltage. Going by the designer's parts list, the LEs supposedly use Texas Instruments SN65176BP RS-485 transceivers to handl e the RS-485 bus, but when I look at the devices, they actually have STMicr oelectronics ST485BN chips installed. I'm wondering if the SN65176BP chips would have better sensitivity, and if I obtained some of them and plugged them in if the devices would

ative 8 pin DIP RS-485 transceiver which might work with the lower voltages ?

it is RS485 from USB, there is no RS232 involved

-Lasse

PTP. The output from his dongle is 12V PTP. It appears the Lynx express does not like the lower voltage. Going by the designer's parts list, the LEs supposedly use Texas Instruments SN65176BP RS-485 transceivers to handle the RS-485 bus, but when I look at the devices, they actually have STMicroelectronics ST485BN chips installed. I'm wondering if the SN65176BP chips would have better sensitivity, and if I obtained some of them and plugged them in if the devices would start working with the lower voltage? Does anyone know of another alternative 8 pin DIP RS-485 transceiver which might work with the lower voltages?

Yes, a real RS232 converter will produce at least 10volts or more.

12 volts was the normal for years.

In the old days the serial port was expected to be able to handle up to

25V if such voltage was introduced, but connected equipment that sits on the RX and TX lines were expected to trigger around 2.5V +/-

Also beware that some equipment required the +/- signals where some of these junk serial converters are not doing that.

It is also possible that the device is using one of the control lines as a switch to enable it, in this case, 10 or more volts maybe needed, which isn't a problem in a real serial port.

I have seen inline aids marketed just for these cheap converters that do two things, they bump up the voltage where they need to be and also offer isolation.

Getting RS232 full line isolator may correct your problem, since it needs generate the output.

Jamie

6V

would

Then he has something wrong. 485 does not operate on such high voltages, at least the specs I've lived by don't. Maybe he's missing the power supply pin that come on many of them.

Jamie