| ??? 08/12/11 12:31 Modified: 08/12/11 12:34 Read: times |
#183328 - AVX varistors... Responding to: ???'s previous message |
Lukas said:
I will put the cap as you suggest. Do you know where I can find this kind of information (about the cap)? I didn't find any reference in the datasheet. Friends of mine failed the CE test because of this! http://www.tracopower.com/products/...cation.pdf Lukas said:
So you suggest me to replace ADM485 by LTC1487 and remove the transils, FBs and pull-down and pull-up resistors... It looks like interesting but if no driver is connected on the line, is it not necessary to define voltage levels by the R8 and R9? In the case of lightning, is the internal ESD protection sufficient? The transil can suppress up to 600 W of power... Thank you very much for your answer in advance... If surges is an issue I use the LT1785, which can withstand overvoltages of up to +/-60V and put AVX varistors like VC080514A300 from the lines to signal ground. This varistor has a considerable higher threshold voltage and due to this much lower capacitance (about 300pF): http://www.avx.com/docs/catalogs/tguard.pdf Of course, you can also use transzorbs with higher threshold voltage then and by this also reduce this unwanted capacitance. But make no mistake, proper surge protection needs the use of screened cables with the cable screen connected to protection earth at all ends. To avoid hum loops signal ground must not be connected to earth directly, but via 10nF/1kV cap, where the cable enters the chassis and the cable screen is connected to protection earth. It's also important to have low ohmic paths in the signal grounds between the RS485 partners. So, the inserting of these dozens of 100R resistors in the signal grounds as in your scheme is no good idea. Kai Klaas |
| Topic | Author | Date |
| Problem with RS232/RS485 converter... | 01/01/70 00:00 | |
| More info please | 01/01/70 00:00 | |
| probably | 01/01/70 00:00 | |
| more info... | 01/01/70 00:00 | |
| yes,i think | 01/01/70 00:00 | |
| input impedance | 01/01/70 00:00 | |
| i'm wrong | 01/01/70 00:00 | |
| what is the right value? | 01/01/70 00:00 | |
| did You tryed capacitor? | 01/01/70 00:00 | |
| thanks... | 01/01/70 00:00 | |
| it works...! | 01/01/70 00:00 | |
| congrats | 01/01/70 00:00 | |
| shape | 01/01/70 00:00 | |
| dont | 01/01/70 00:00 | |
| It is OK. | 01/01/70 00:00 | |
| Hints... | 01/01/70 00:00 | |
| schema | 01/01/70 00:00 | |
| Repair... | 01/01/70 00:00 | |
| transils... | 01/01/70 00:00 | |
| RS485 | 01/01/70 00:00 | |
| Sample Schematic | 01/01/70 00:00 | |
| Thank you very much for the schema... | 01/01/70 00:00 | |
| AVX varistors... | 01/01/70 00:00 | |
| capacitor | 01/01/70 00:00 | |
| capacitors... | 01/01/70 00:00 | |
| GNDs | 01/01/70 00:00 | |
| 1992 | 01/01/70 00:00 | |
| Thanks... | 01/01/70 00:00 | |
Links... | 01/01/70 00:00 |