help me with building a power supply.

Hi, im building a power supply for an eprom programmer , the whole project can be found here in this website
**broken link removed**
i ve uploaded the power supply shematic in question ,as you can see this psu needs two relays RL1 in green ,and RL2 in red ,the person who designed this psu says that both coil relays have to be 1300 ohms 24v 4 inverters contact.i ve searches ,and could not find the right relay on internet to buy so my question is what relay do you recommand to put in these positions RL1 RL2 ,which one should i buy sorry im not engeener or electronician expert, thanks in advance.

The relays are switched by transistors, so the 1300 ohm coil shouldn't be critical. 24v/1300 ohm = 18mA, so if you're somewhere near there, they should work fine.

coil voltage: 24
coil current: 15 - 25mA (1600 ohms - 960 ohms)
contacts: DPDT (same relay will work for both)

The picture shows some options from Digikey.

vari21 said:

what relay do you recommand to put in these positions RL1 RL2

Click to expand...

You could try one of these:



The designer of this EPROM programmer is relying on the resistance of a relay coil and the value of an electrolytic capacitor to to provide a time delay which he thinks is critical to the correct operation of the programmer.
He specifies a coil resistance of 1300 Ohm, at a quick search I can only find relays with a coil resistance of 1280 Ohm, that should not affect the timing too badly.

JimB

JimB said:

You could try one of these:

The designer of this EPROM programmer is relying on the resistance of a relay coil and the value of an electrolytic capacitor to to provide a time delay which he thinks is critical to the correct operation of the programmer.
He specifies a coil resistance of 1300 Ohm, at a quick search I can only find relays with a coil resistance of 1280 Ohm, that should not affect the timing too badly.

JimB

Click to expand...

Better answer than mine.

Thanks you jim and visitor for light my way, ,sorry for asking to much ,but i m still confused on how to wire the relays on pcb ,the guy who made this design said that the relay must have 4 pairs of contact 4 RT (R for repos) (T for travail) repos =rest travail=work
so im wondering if 24v dpst with only 2 pairs can work or not.
im not located in uk so i can buy from uk suppliers .thanks again

vari21 said:

so im wondering if 24v dpst with only 2 pairs can work or not.

Click to expand...

No, a dpst relay will not work for RL1, but could be used for RL2
For RL1 you will need a spdt, but a dpdt will work just as well, you only use one of the poles.

vari21 said:

the guy who made this design said that the relay must have 4 pairs of contact 4 RT (R for repos) (T for travail) repos =rest travail=work

Click to expand...

OK I will try to explain.
Look at my annotated PSU diagram:



RL1 is what we call in English a "single pole changeover relay"

RL2 is what we call in English a "two pole changeover relay"

Each pole of the relay has two contacts:
Normally Open (NO) (en Francais TRAVAIL)
and
Normally Closed (NC) (en Francais REPOS)


Look at the datasheet for this relay



Look at the layout of the electrical connections at the right hand side of the above picture.
There are two poles each with two contacts.
This relay can be used for both RL1 and RL2 in your programmer PSU.

I hope this makes sense.

JimB

Jim you re a master, thank so much i ve got it now ,thanks for your time.

Wow, praise indeed!
Thank you.

JimB