Saturday, May 27, 2017

Blue gateway 1.7C

A picture is worth a thousand words. Here is new OHS gateway officially named 1.7C. Major difference comparing to 1.7. is 2G modem SIM800C. With four bands GSM support it can be deployed worldwide. And just one remark to relays, I have switched from black Chinese made Omron to blue one's made in Japan. They are slightly more expensive, but somehow cute and blue :).

Friday, May 26, 2017


New nodes now come with blue PCB and as option with USB charger. Here on picture you can see battery powered node with USB charging circuit and temperature sensor. On back there is RFM69HW module, also available as option, and 720mAh Li-on battery. Such batteries can be found on ebay. They are sold for quadrocopter toys, and even they are labeled as 25C RC, they have build in protection circuit.

Further more I will, or I can, equip all battery powered nodes with 8MHz crystal oscillator instead of 16MHz. This reduce the power consumption even more. The whole setup on picture has following consumption:

ATmega328P@8MHz sleeping 33.2~33.6uA
ATmega328P@8MHz running ~4mA

Just to ones that are curious what are the missing components. This board can be either battery or DC powered, and also can communicate over radio(RFM69HW) or RS485.

Thursday, May 18, 2017

Blue gateways

The life of components in electronics can also come to an end. So is true about SIM900 GSM modem that is part of GW version 1.7. Although it is still available online, officially it is not recommended for new development, and local distributors have no longer any in stock. The decision had come to choose new GSM module. As SIMCom modules have proven to be reliable at good price, I had in mind to switch over to some of their new model. Put it simple SIM800C was chosen to be a replacement. It is still 2G modem with four band GSM support and can be deployed worldwide. Fortunately there is no difference in AT command set that is used by gateway firmware, so the new boards are interchangeable in terms of code. There seems to be interest in 3G modem of OHS gateway users that are located in U.S.A., but for now we stay at 2G (3G module is 4x expensive then 2G, and 3G band are varying across regions. But if there will be interest, I will design new version of gateway with possibility to mount 3G or 2G module).

New boards have also same footprint and connectors location have not changed, except for SIM card holder and GSM antenna connector. They are named 1.7C and come in blue colour with round edges similar to new nodes.

P.S. Picture will come soon :)