- Sat Sep 11, 2010 1:02 pm
#109312
Hi,
I need to design a power supply for an Xbee device. The device is powered from 24v and I must say I am a bit lost selecting the right components. My device is just a Xbee device with a RS232 connection. Because my application is industrial I want to use a fanless enclosure which is aluminium.
Here is where I am now:
First I tested using a linear power supply with the LM317. I worked, but the heat generated was excessive and I don't have room for a large heatsink (and I don't have a fan so the heat can't really go anywhere).
Then I wanted to use a switching power supply (based on the mc34063), but read in the Xbee documentation that when using a regulated power supply the switching frequency must be at leat 500kHz and the ripple must be no more than 250mV. However, the components that match these criteria are all tssop or smaller packages and are normally regarded to be rather advanced...maybe not the best choice for my first real-life project.
On the other hand, using a good switching power supply will probably generate the least amount of heat because they are very efficient.
My in-between solution is to use a simple mc34063-based switching power supply, step down the voltage to around 4.5v and use a LD1117V33 (a low dropout linear regulator) to get to a stable 3.3v to drive my circuit and xbee. So basically I would be mixing high and low efficiency and the resulting efficiency will probably be rather good, while using simple and cheap components.
My question: does anybody have experience designing such a power supply? Should I invest more time in the switching power supply or is my mixed solution ok? Maybe the mixed solution still generates too much heat (I use the XBee Pro module and my total circuit can use 500mA), but I haven't been able to test it yet.
I'm very interested in what you think. This is my first project, so please be gentle with me
I need to design a power supply for an Xbee device. The device is powered from 24v and I must say I am a bit lost selecting the right components. My device is just a Xbee device with a RS232 connection. Because my application is industrial I want to use a fanless enclosure which is aluminium.
Here is where I am now:
First I tested using a linear power supply with the LM317. I worked, but the heat generated was excessive and I don't have room for a large heatsink (and I don't have a fan so the heat can't really go anywhere).
Then I wanted to use a switching power supply (based on the mc34063), but read in the Xbee documentation that when using a regulated power supply the switching frequency must be at leat 500kHz and the ripple must be no more than 250mV. However, the components that match these criteria are all tssop or smaller packages and are normally regarded to be rather advanced...maybe not the best choice for my first real-life project.
On the other hand, using a good switching power supply will probably generate the least amount of heat because they are very efficient.
My in-between solution is to use a simple mc34063-based switching power supply, step down the voltage to around 4.5v and use a LD1117V33 (a low dropout linear regulator) to get to a stable 3.3v to drive my circuit and xbee. So basically I would be mixing high and low efficiency and the resulting efficiency will probably be rather good, while using simple and cheap components.
My question: does anybody have experience designing such a power supply? Should I invest more time in the switching power supply or is my mixed solution ok? Maybe the mixed solution still generates too much heat (I use the XBee Pro module and my total circuit can use 500mA), but I haven't been able to test it yet.
I'm very interested in what you think. This is my first project, so please be gentle with me