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Can anyone help please?

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karenhornby

New Member
WhaT i want to do is program a DS1620 chip
However the only program/circuit I have to program it is THIS **broken link removed**
It is powered from the serial port but as I have a usb-serial convertor I'm pretty sure it wont have enough current to drive the programmer properly
Can anyone "convert" the programmer on the above link to work from 5v? i.e. remove anything that isn't needed if I have a 7805 connected to the chip to supply it with 5v BUT still be able to talk to the computer and be programmed?
 

3v0

Coop Build Coordinator
Forum Supporter
Karen. Nice to see you back. This chip is general used with a microcontroller. There is not high current or voltage associated with programming the chip. If it will not work thiw the USB to RS232 converter it is because the converter is not converting or is doing a poor job of handling the control signals DTR, RTS, and DSR. Not uncommon.

Dallas also makes a series of 1 wire chips that may be easier to use. Maybe if you can share the application we can better help you. How did the previous project work out ?
 

karenhornby

New Member
Yes thanks, it worked perfectly :)
HMM basically what I'm trying to do is monitor 2 different temperatures and output light an led when the range is between set limits on both.
I thought this chip would be easy to use because it can be set to "thermostat mode" with just one pin going high when the temp is between the ranges set.

My other option is using 2 ds18b20's but as I dont fancy trying to figure out one wire bus protocol and how to interrogate the chips to see which chip is which and then figure out how to address each one seperatly, IF I end up using these then I'll probably just use 2 and dedicate one pin of a pic to each if that makes sense
SO it would actually be easier IF I could get these ds1620's programmed, but short of buying a decicated serial output board fed from the pci bus It's a matter of trying to get the circuit I have working somehow, I was hoping to get it working by using a 5v psu instead of powering it from the serial port
 

karenhornby

New Member
Oh while I think about it, anyone got any suggestions on a SIMPLE circuit that will drive a solenoid from a pic output (16f877 probably) the solenoid draws about .6A at 12V
I'd prefer not to use relays if possible for neatness
 

Pommie

Well-Known Member
Most Helpful Member
You can easily power the circuit by connecting a 5V supply across C2 but I doubt that is your problem. My USB to RS232 converter does not switch DTR and I think this is more likely to be your problem. Can you borrow some different converters to try?

Mike.
 

3v0

Coop Build Coordinator
Forum Supporter
I understand why you would like to use a PC to set it up. Can you find an old PC with an RS232 port? Skip the converter.

If you are going to put this on the system with the pic use the pic to setup the DS1620. It uses a 3 wire interface that is not too hard to program.

On the 1 wire stuff there is a command called skiprom you can use if there is only 1 sensor on the bus. It tells the device to use the next command without checking the address. Not quite as bad as you were thinking.

There are others who are much better able to help you with the solenoid question. I am thinking a mosfet that is rated at about 2 amps. But I am guessing. If I am wrong it will get the attention of a body that knows better :)
 

karenhornby

New Member
Thanks guys :)
I've found this pic (attached) which is a dead simple circuit but if I was to use a tip32A (higher current rating just to be on the safe side and should run pretty cold at 600mA) what resistor would I need? I know I should know this but it's throwing me because The pic is being supplied with 5V obviously, but the solenoid is being switched by 12-14V from the car battery
I decided to use the pnp transistor because then I can run only one wire to the solenoid and connect the other end to the car body (ground) rather than having to run 2 seperate ones with an npn one.
Although I would have preferred to have switched it on the pic pin goinng high, I cant actually see a problem switching it by the pin going low.

The other option I was thinking of was using a darlington transistor/array as I'll be using 2 solenoids but not sure how these would work as ideally they'd have to be rated at around 1A current rating just to be on the safe side even though I'll only be drawing 600mA (ish) through them
 

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Pommie

Well-Known Member
Most Helpful Member
Using a PNP is not a good idea. There is a path from the 12V line through the transistor/resistor and into the pin of the pic where a (protection) diode will conduct it to the 5V rail. Use an NPN and a base resistor that drops 3.5V at the current that is 600/hFEmin mA. If the current works out at more than 20mA then get a transistor with a greater hFE.

Using the 2N2222 and Bills figures above, the base current would be 600/50 = 12mA and so R=3.5/0.012 = ~300Ω (The 3.5V comes from the Pics output voltage (4.3) - Vbe (0.7) which is roughly 3.5)

If you really want to keep to one wire then a second (NPN) transistor could feed the base of a PNP.

HTH

Mike.
 

karenhornby

New Member
What do you reckon then to a TIP41A?
any idea what resistor if I was to stick 12v on it but drive it from the 5v of the pic?
sorry I know I'm asking dumb questions that i SHOULD know the answer
 

karenhornby

New Member
Scrap the above, I've decided it's going to be simpler to use relays!
sorry would have deleted or edited but it didn't give me an option for that!
 

Hero999

Banned
You can still use transistors if you like, you just need two to switch a +12V supply with a PIC.

Make R3 220:eek:hm:

**broken link removed**
 
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