I am looking for something simple that has:
0) 24 pin socket compatible with the ZX24/ZX24a
1) regulated 5VDC power supply
2) real RS-232 level port for the com1 hardware uart port
. . . . (rather than a disclaimer)
3) No extra memory, solenoid controls, or other extraneous hardware
Have I missed something somewhere
I really do not want to re-invent the wheel.
I believe that all of the carrier boards that you listed meet all of your criteria except for #2. I haven't seen any carrier board that provides true RS-232 levels and also accepts a Stamp-format device.
If having true RS-232 levels is of utmost importance you might want to consider Oak Micros' ZX line. However, they are 40+ pin devices and won't fit the carrier boards that you listed. On the other hand, I've found the solderless breadboards to be a better development solution than using carrier boards.
Last edited by dkinzer on 28 October 2007, 10:26 AM, edited 1 time in total.
dkinzer wrote:I believe that all of the carrier boards that you listed meet all of your criteria except for #2. I haven't seen any carrier board that provides true RS-232 levels and also accepts a Stamp-format device.
If having true RS-232 levels is of utmost importance you might want to consider Oak Micros' ZX line. However, they are 40+ pin devices and won't fit the carrier boards that you listed. On the other hand, I've found the solderless breadboards to be a better development solution than using carrier boards.
Looked at the OakMicro but from what I have seen one would have build a board for those as well. I have the project done on a bread board. I just want to copy it (6 times) to something a bit more permanent and less exspensive. I was suprised that there was nothing available with true RS-232 levels. Figured that I has just not found it ... oh well.
lewtwo wrote:I have found the following sources for Carrier Boards (for the ZX24a):
I am looking for something simple that has:
0) 24 pin socket compatible with the ZX24/ZX24a
1) regulated 5VDC power supply
2) real RS-232 level port for the com1 hardware uart port
. . . . (rather than a disclaimer)
3) No extra memory, solenoid controls, or other extraneous hardware
The fault lies less in the boards and more in the fact that a ZX-24a does not fully support RS-232 levels. This is mostly because of lack of space on the ZX-24a device. I think that is why Don suggested using the Oak Micros ZX-24ae which has a proper level converter.
Perhaps it might be better to use a ZX-44a/ZX-40a and supply your own circuitry as Tom suggests. You don't tell us if any other circuitry is needed so we cannot help you much. Depending on your intended use you could use stripboard rather than a PCB. This article (which I wrote some time ago) explains how to use Eagle and stripboard http://tinyurl.com/2mhauo
>> You don't tell us if any other circuitry is needed so we cannot help you much. Depending on your intended use you could use stripboard rather than a PCB. <<
Actually none (everything else is external). That is one reason I was really looking for a ready made dev board. Another option is to use one of the aforementioned dev boards and a RS-232 level adapter like: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0174540781
As it turns out I decided to use the OakMicro devices and ExpressPCB. I must say that I was very impressed with ExpressPCB. It has been at least 20 years since I laid out a board (some of the grey cells have gone dark) via tape and pads. Things have come a lonnggggg way.
The depth of my ignorance of low level hardware is difficult to fathom . One of the things that I do not understand is the diode between the output and the input of the 7805 on the suggested power supply circuit for the ZX-24. Seems to me it would only come into play when external power was lost.
lewtwo wrote:One of the things that I do not understand is the diode between the output and the input of the 7805 on the suggested power supply circuit for the ZX-24. Seems to me it would only come into play when external power was lost.
Yes that is exactly right. The diode protects the 7085 from a reverse current when the power is switched off.
You may also want some protection from accidentally reversing the input co connections by placing a diode on the input side. Note that the input voltage will drop by 0.7V (or whatever the forward voltage is of the diode).
When driving higher current loads, it may be advisable to also attach a heat sink to the regulator. Remember that the power dissipated by the regulator is
If Vin - Vout is large you may want to consider a switching regulator that is more efficient and dissipates much less heat. If Vin - Vout is small (< 1.5V) then a LDO regulator will be needed.
lewtwo wrote:One of the things that I do not understand is the diode between the output and the input of the 7805 on the suggested power supply circuit for the ZX-24.
As Mike indicated, it is to protect the regulator. The diode is recommended by the manufacturer in cases when the capacitance on the output side is higher than the capacitance on the input side. In this circumstance, when the power is removed the voltage level on the output side will take longer to decay. This may result in there being a higher voltage on the output terminal of the regulator than on the input terminal - a situation that can damage the regulator.
. One of the things that I do not understand is the diode between the output and the input of the 7805 on the suggested power supply circuit for the ZX-24. Seems to me it would only come into play when external power was lost.