easy-Forum, first offical forum with topics concerning the easy control relay, EASY-SOFT

The connection between most PCs and the EASY functions perfectly, while other PCs refuse steadfastly to establish communication. This problem particularly seems to affect Laptops which are not equipped with their own serial interface, and which then use »USB to serial« converters.

The reason could be due to the electrical isolation between the EASY and the PC, which is intended primarily to protect the hardware. The PC provides electrical power to the serial interface with the aid of the control lines to ensure electrical isolation without using a power supply. This is the standard approach with very small currents. I presume that the components in the converters have been developed with consideration of current saving and cost saving aspects. They may not be able to supply this current or use the particular features of the serial interface. They do not generate negative control voltages and only function with the positive voltage and ground. With this variant, the voltage increases on the negative voltage line and it becomes a positive voltage so that the same voltage level is always present on the receiving input of the PC. A third problem is caused by bugs in the drivers. (The control line which should become negative remains positive.) Depending on the operating system, the USB adapter may or may not function.

The following circuits could help. They worked for me.

The following two variants can be used for those of you whose control lines are not supplying enough current or who just want to make sure:

Photos of my prototype:

A small 12 Volt power supply is now required which supplies the opto-couplers for the electrical isolation.

On the move, it is not always possible to find a socket to plug in the power supply. Instead of a power supply, it is possible to use a 9 V battery which ensures full independence from an electrical socket. Theoretically, it can be used continuously for approx. 100 hours. (When it is not used, the PC-CAB should be removed from the adapter as otherwise current will continue to flow!)

Photos of a variant suitable for everyday applications:

For those who find the battery or power supply variant too much bother, a cheap solution can be used:

Connect the negative control line of the PC-CABS (PIN 4) directly to ground. If the current of the positively switched control line is sufficient, this variant can be used.

A concluding comment: There are also differences between the individual converters due to the drivers. A download takes much longer at the same baud rate on some converters than it does with others. It can even occur that the transmission time will remain constant even when the baud rate has been doubled.

Unfortunately you have to purchase a number of converters in order to determine the best configuration between the PC and converter.
(Of course, I cannot accept any responsibility for damage of any kind regardless of it being direct or consequential).

Greetings, Otto Birr